Comparison of the Sonar-GPS combo units for small craft Irish angling:
Last year's 2008 sonars from Lowrance, Eagle, Northstar and Navman all had similar downlooking display quality. IMHO these makes are better than Garmin or Humminbird as measured by relative clarity for this function (looking downwards). Looking down is the first and primary function, everything else is an add-on, or a distraction, or an improvement.
GPS will get you back to the place you want to be. The GPS WAAS ability is (sometimes) accurate to 10' which beats the usual 30' accuracy. So WAAS is necessary.
It seems to me that everyone says "their make" is the best. But based on stories I've heard, and I work beside people in the boating trade, (accuracy - bias??) Both Garmin and Lowrance seem to be well regarded for accuracy. Many Garmin users say theirs is easier to learn.
Navman and Northstar have very clear screens too, but these makes use C-maps which are less accurate for Ireland at present, so I would leave their GPS units, though their sonar units are excellent.
Humminbird, Lowrance, Eagle use the more accurate (in Ireland) Navionics Platinum maps and these cover the Shannon and Erne. These maps include underwater contours, but unfortunately do not go tight into the shoreline , concentrating on the middle sections of the loughs mapped.
Lack of commercially pre-made lake maps in Ireland places a greater need for the ability to make your own angling maps, more than other countries where freshwater maps are available in boat and tackle suppliers.
You can make lcm maps only for Lowrance/Eagle right now.
Garmin recently changed their map file format and I am not sure if we can do our own maps yet, but I am sure the software will soon be hacked by enthusiasts and the freeware Mapedit amended to do it again. Watch for progress if you like Garmin.
Only Lowrance and Eagle allow you put your self made map back into your sonar-GPS unit, so you can plot where you are on your map.
Only Humminbird 700/900/1100 SI series have an affordable look-to-the-side function, and this is the next most important function.
Fishin Buddy has a low cost side scan, and Interphase Color Twinscope 90/ISCAN 180 provide a higher cost semi professional side scan. But these don't make the photo of the lake bottom that the side imaging Hummminbird produces. However Fishin Buddy and Interphase DO give an ability to look around, and ahead of the boat, which the Humminbird does not do.
Many anglers are fascinated by a side image photo of the bottom just passed over (Humminbird style) more than a radar view of the bottom ahead. In truth and speaking carefully I am unsure which is worth more. Both need careful study so as to interpret them and get the most information from what is a confusing display screen if looked at carelessly.
The reason I'm unsure which is more useful, is that locating cruising trout nymphing in midwater while drifting in a boat/tube is impossible with side imaging style units, but the radar style unit can do this superbly. This is a big leveller if the unit is to be used while fly fishing, or casting lures and drifting. And it moves the less romantic Interphase up in value even though I find the nice Humminbird SI screenshots amazingly seductive. The radar view of a cruising, or several big trout cruising towards me midwater from 50 metres away enables a crucial cast or two over them before they come close, and if they don't rise and show themselves, the Interphase is the only chance of an accurately placed targeted cast with a weighted nymph.
The way a 797/997 overcomes this is to troll past an area, locate the fish, and then go back more accurately, provided they are still there. I believe that the HBird SI is a great trolling tool for locating static fish, and a Color Twinscope horizontal scan is a great drifting/static tool for casting to moving fish. It's a difficult choice.
For me it is clear that with all side view instruments, a big screen beats a small screen, since sideways detail is compressed so much and becomes so tiny and hard to see. Unfortunately big screen = cost!
NMEA0183 data down a cable from the sonar is essential to make your own maps, Lowrance, Humminbird, Eagle, Interphase, Northstar, Navman, Garmin all export this data, but Fishin Buddy does not. Check the unit is high enough in the maker's range to include the feature.
If using side image with humminbird, the map goes into a handheld PDA, and you don't use the map that comes on the HB. So it's 797 + PDA.
If using look down with Lowrance - Eagle, the map is inside your waterproof sonar-GPS unit, or on your PDA, whichever you want, or both.
Sonar-GPS 2009 units vs 2008 units?
In 5" screens, the interesting ones are the LMS 522c, it's new 2009 replacement model the HDS5, Eagle 642c, and the Humminbird 797c2si and it's2009 replacement 798cSI
On the other hand, the 2009 new units have caused a fall in the prices for the "old" 2008 units as big sellers try to wind down their stocks fo these particular units. Big price breaks are not to be sneezed at.
Sonar features available for 2009
The new Lowrance has the broadband sounder (LBS-1) built in which removes surface clutter almost completely. Also it will only consume 1/10th of the power that it used to, and therefore will go a lot longer on small batteries, and therefore portability and weight are going to improve with this unit. This really suits me for use in my float tubes.
Despite using small batteries and less power it will show more detail than before, and reach deeper than before. A Broadband Sounder unit shows more detail on just 250Watts than was previously possible with 2400Watts. (By comparison the Eagle 642 is 1500W and the HB 797c2si is 4000Watts so they need bigger batteries for a day's/weekend's use. ) I like the idea of a transducer that whispers rather than shouts, because I always believed the fish were aware of the pings. After all I can feel them when resting the xducer on my hand, and hear the clicks when listening carefully, and a fishes lateral line is incredible sensitive.
The 2009 798 series Humminbird has the same side imaging as before, but now can take two SD cards, so it can record and display a Navionics map simultaneously, something only the bigger units could do until now. The screen got more pixels which is a good thing for showing details.
My Setup for the 2009 Season
With an unlimited budget I would use both Lowrance for GPS and down view, Humminbird SI for looking out sideways, and Interphase for looking ahead! If only!
A strong temptation is a Lowrance with a Humminbird SI, and disable the downlook ability of the HB.
On cost grounds I decided to get a 2009 Lowrance HD5, and use it together with my present Interphase scanning unit (set on horizontal). The next time I can upgrade the Interphase if I feel it's necessary.
Background info here:
The LBS-1 which is inside the new Lowrances:
These are my opinions, others may disagree. I did check out the subject matter very carefully and try to stay up to date with the latest information on this subject. I try to avoid fooling myself that the unit I currently own, and have invested my cash in, is the best, or that that make is the best. It is an easy trap to fall into, undeserved pride in your current gear.