I'll be upgrading my sonar soon and want some opinions on the above units. The Lowrance unit seems pretty reasonable considering it has 320 X 320 graphics compared to Garmin's 240. According to Lowrance's website, X-88DF is comparable in every other area such as power output, transducer, frequency, etc.

My other question is how important is having a duel frequency for the salt? I ask because I only fish the salt for a couple months in the summer for kings and coho. I target fish in less than 150' of water. Is it really worth paying the extra money (albeit only about $50) for the dual frequency in that situation? The rest of the time I fish freshwater lakes and rivers.

How many of you with dual frequency units always use the split screen and monitor both freqs simultaneously?

GoHarley, Have you looked at the Eagle 320DF yet? it is basically an X-88DF without the flasher feature. Same specs otherwise, 500watt RMS, dual frequency, speed and temp, and 320 x 320 pixels, it is basically a 240 Blue selling for the price of the 160 Blue, $240.
I get asked at work 2 or 3 times a week which is better, Garmin or Lowrance/Eagle, I don't honestly think you can go wrong with either, up until 3 months ago Garmin far outsold everything else but since Lowrance/Eagle came out with their new products (priced to compete with Garmin) I couldn't tell you which is the best seller, its very close.
As for your question on dual frequency, its a must in my boat, single frequency units are generally 200 khz (actually 192khz) and narrow beam, 10 to 20 degree usually which isn't much coverage, dual frequency units give you a 50/200 khz beam that covers alot more area, usually from 40 to 90 degrees depending on brand.
Before you buy, checkout the Eagle.

I've owned both garmins and lowrance. You cant go wrong with either. Eagle is made by lowrance so you should'nt go wrong there if thats what you decide. I have never had any problem with a single frequency unit in the salt and I fish it exclusively. The 50 khz is supposed to help you read deeper but my 240 has no problem reading the bottom to 700' with a 20 degree transducer,which is way deeper than most people fish here in the sound. Hell I very seldom fish bottom deeper than 150' unless I'm after bottom fish. Hope this helps.

Thanks for the help, AKKINGS. I hadn't noticed the Eagle unit before, but I see that it is very comparable. Looks like it will be on my boat real soon since SWMBO blessed off on it as a birthday gift.

As stated earlier, Eagle and lowrance are the same company. I currently own two Eagle fish finders and one GPS/fishfinder. I have had trouble with all three. One FF is 6 years old. It has been back to the factory twice for repairs and is now dead. The factory says it's now too old and will not work on it. My newer GPS/FF kept shutting off for no reason (I verified a good power supply). The factory could not fix and sent me a new unit at no cost. Now, the unit has a thin line through the LCD display that will not work. This unit was made in Mexico! I will not buy any more of thier products. I have three friends that have Garmin units and have had no problems whatsoever.

I have one big ***** about my new garmin 240 blue. No actually several. Do not expect this unit to show any fish as arches. Do expect to see schools of bait marked as large columns of fish. Thermalclines will also show as fish. I have never spent so much time fiddling and adjusting and dialing in a fish finder in my whole life! Never have gotten any concrete feedback/answers on adjustments. If anyone else can absolutely tell me what is going on, I would like to hear thm speak up. Not what I expected for the money.

Juggernaut sounds like you have your fish ID feature turned on. Shut that off as its only purpose is to catch fishermen. The only time any of my units have shown fish as arches is when I'm in very shallow water or the fish are shallow under the boat. It's a scale thing. A fish down 70ft in 100ft of water is going to be projected on your screen at a scale proporional to what you have set on your unit. It's only going to show up as a dot or two depending on how big it is. Bait fish schools show up as clouds.

So chaser, just one question. With the fish I.D. off, what kind of "marks do your fish or bait balls show up as? I have run the unit with the symbols off as well, but have not seen good readable fish marking. What does your f/f show?

As I mentioned before bait balls show up as clouds or dark spots on the screen where individual fish show up as a dot, line or dark spot depending on how big the fish is. very seldom do they show up as an arch. The pixel counts just wont allow it and still keep the scale in perspective. I also have an X-15 paper graph which is known for its ability to show great detail but it also does'nt show every fish as an arch. I would'nt get too hung up on trying to see every fish. Over 90% of the fish I've hooked never even showed up on on the sounders as they were outside the cone. I Mostly use mine to find bottom or the depth at where the majority of the bait is.

I think that I finally have enough information to make form a educted opinion. After speaking with the various sales people, garmin reps., 240 owners, and other assorted experts; it looks like I purchased a unit capable of reading the bottom and showing large bait balls. But, I shouldn't expect it to show individual fish accurately, or if it does they could be shown as a dot or line or something.
The only problem is that I purchased the Garmin to give me a better picture than my hummingbird(good thing that I did not remove the HB).
The 240 blue seems to be a f/f trying to fill a cost gap between the cheaper units and the more expensive ones. I'f I had it to do again, I bet that for just a few dollars more a 340 by 340 unit would have been the way to go.

Now you got it! Go for the 2 to 3 thousand dollar unit, you'll be much happier from the sounds of things. Of course the ones I've seen being used on charters did'nt show the fish as arches either! What then, 4 - 5 thousand dollar units? I would think a more realistic view of a fish finders capabilities and then learning to interpret the info your viewing would be a better alternative. My .02s. Good luck trying to find those arches

Last note: Garmin was the one advertising arches on the 240 blue.... obviously deceptive (that was my point). As far as learning to decifer a f/f screen, I do just fine. I think the bottom line on most inexpensive units(ie. under $1000 or so) is that they are all basically the same. If all you want to do is mark the bottom just spend a couple hundred dollars.