One difference is the pixel matrix to display size. I was looking at the Helix 5, 598, and 698. All in the same price range at the time. Best thing I did was go to Basspro and look at them all turned on. Helix 5 with 800v x 480h on a 5" display looked awesome but was too small for me to see because it was laid sideways. The 698 with 480h x 640v 5" display looked bigger the way it was turned but was too poor quality pixel to make out fish on SI. The 598 with 640v x 640h 5" display also laid out like the 698 was just right with the higher pixel matrix. Now I haven't looked at the Helix 7 but with a bigger display it might be really nice. The bigger display the better when it comes to SI.

Is it worth the extra money? For my getting older eyes it is.

IMO, just should buy one size bigger than you can afford, it only hurts once!

Should I have any problems in mounting the unit? Transducer?

Ok. Sounds like the Helix 7 is preference of the two.
Now if I can just catch it on sale soon!

And my eyes of 56 yrs are old also.

Should I have any problems in mounting the unit? Transducer?

Topwater here is the review I did on the Helix 7. It is on my hobie PA. Great unit.

First want to say thanks to David at Shut up and Fish. Great guy to work with and will answer all your questions.

Helix 7 SI. Was using a 2 year old Lowrance DSI that the tech is probably 4 years old so this is not an apples to apples comparison.

Pro's
SI was as good as promised. Being a crappie guy looking for BP's I can see this making it much easier to find new piles. Very good image. The experts say to upgrade to the HDSI transducer but I am too impatient to wait so used the compact, that comes with system. Will say Doug Vahrenberg's tips say to put SI sensitivity to 10-12. I will say on soft bottom 10'-20' 11 at least and deeper you may need 12-13 otherwise it is a little too dark (for me). I thought the transducer produced very good, easily recognizable images.

Bright, bright screen.

DI. I know they use side pulses to get the DI but out of the box I didn't think they were great. Will try different settings next time to see if I can improve image on DI.

Sonar. Not having sonar on my last one I wasn't sure I would miss it. I really don't miss it that much. Fish ID. Humminbird experts say that it works very good. I did see a few fish in submerged trees and caught one at that depth. Now I fished that tree cause I usualy catch crappie there. Will have to find a new to me pile, see if any Fish ID's show up and see if crappie are at the stated depth. If it works it will markedly improve my catching. Maybe grin

GPS. SO MUCH BETTER than old one. It is very responsive. Did some test and usual was 1 second response. On old one would have to approach waypoint from 20-30 yards away to get good location cause it wouldn't update fast enough. Now as soon as you can turn around you can go right back to way point.

Cons. Come on HB, what is with the sd card slot. 1st the door completely detaches from case. 2nd it is very hard to get card out. I thought about bringing a blank card out and getting screen shots but am afraid I might lose Navionics card or door if not extremely careful. bang

Install is on PA and you can find a thread on Hobie PA forums and I followed that guys steps for making a retractable transducer mount in the transducer pad for PA's. Pretty easy if you are good with dremel. I am not.

I think this will help me on crappie fishing and getting better idea of what is below me. I think either 5 or 7 will work great for yakers. Will update when I get more time on the water with it.