The Ti2 has the ability to pair with another Ti2 vis Bluetooth. It also has NMEA capabilities to connect to other Lowrance graphs. Also right now you can a 9" Elite Ti with totalscan transducer for only $599 at BassPro and Cabelas

Hook 2 works well. Not a mega by any imagination but very nice for the price.

ease of use, best bang for the buck, garmin imo

more options on expansion later without having to change things. ran birds only since my first flasher in late 70s and garmin has them beat with the touch screen, wifi/phone app/updating and features pre loaded.

only thing I have to add to my 93sv plus is a map upgrade for some extra features. very happy with them.

I ran Lowrance HDS units on my last boat. I've got Humminbird Helix MEGA SI units now. Hands down Helix SI definition is the best.

I went the other way from hopalong, my 'Cat came with a Solix 12 G2 and Helix 12 G3 on bow. Solix 12 G2 has an underpowered CPU, was flaky, and not nearly as good of a touch screen interface as a Carbon/Live, very laggy. It also really can't do SI Mosaic recording...basically period (unless they fixed the flakiness). The SI images were slightly better on the Solix than on my HDS Live now that I have it dialed in, the down imaging was quite a bit better than the Live although I find the fish reveal part of Lowrance's DI technology helpful at times. Navionics runs better on Lowrance units than on that Solix for sure (in my opinion), smoother, less clumsy zoom, keeping up at 70mph etc.
The Helix is not a bad non-touch unit, fast, more stable software, but overpriced in my opinion for a non-touch unit. The networking between the two was flaky, had to power up the Helix first or they wouldn't connect. The birds had very low limits on the number of waypoints that you could have as well. I think the 360 technology (just from seeing videos) is pretty cool, and if you wanted that, obviously the Bird route is better. After talking to Humminbird support, posting up videos of the problems to a dropbox 7 or 8 times, system boards replaced twice, I finally cried uncle and went back to Lowrance. If you were only going to have two units and price was a big deal, as another poster mentioned, Ti2 units. Just my 2 cents from experiences over the past year.

PS. I have a HDS Live 12 out in California at the repair center having the system board that went out replaced...they all have their pros and cons

Toss-up between the Helix and the Garmin Echomap UHD but I give it to the Garmin for being touchscreen and more user friendly. . HDS & Ti2 have some good options but their imaging is a bit behind.