Garmin use their own maps, I took a look at them on their site today pretty cool, cheaper than navionics too by about $100.00.
Navionics Premium East or Hot Maps east, is only 99.00 now and looks great, Old Fisherman just bought one, looks fine for Squam with 1' contours, but I'd check the lakes you want.
Depends what lake you are on, Squam's Garmin map is/was only 10' contours, I dont think it is as good for maybe Sunapee and Newfound, Winni might be OK. Garmin will not accept Navionics chips. The Elite does not offer safety contours I'm pretty sure, I find them very useful. Roger (Fishin Squam Again) had a Garmin, upgraded to the Elite and returned it for an HD5 I think, maybe he will chime in.
If cost is a consideration and it usually is for most of us, I'd look on E Bay, people change fish finders more than you cab imagine, especially Bass guys, one new feature and they trash the old units in a heartbeat, may be only a year old or less, and they always buy at least two.
I don't know what you have now, but I'd look on E Bay for a used HD5 or a LMS 520 series, I run two 520's and love them as I know my way around them pretty good now, if I get stumped Russ Johnson is the resident Lowrance Guru. I'd rather have a good used one that's proven over a newer model that may actually be a step down in some cases..
The LMS 520 series still go from 300 to high 400's, (when new 750.00) the Lowrance hold the value pretty good. But I'd do a little more research on the Elite, I don't think it's what the name implies, ha-ha, but it may be perfect for some peoples needs.
Allot of new boats put in FF/GPS units now and they are great for boaters, but not for fisherman so these guys move them on e bay, buyer beware.
If you buy a used unit on E bay, make sure you get the complete set up, including brackets. That stuff can be bought from allot of after market places but pricey, Lowrance knobs 30.00 for a pair. I have a few web sites that sell that stuff.
Another thing, make sure you have the same color cable connectors if you are going from Lowrance to Lowrance. Newer Lowrance use Blue connectors and the same cables can be used for most any Lowrance units including ducers. Some Lowrance units require a red connector cable adapter for external GPS. By the way, internal GPS antennas seem to be fine, I don't know if you can even get an external one anymore. If the external GPS module fails, they cost 250.00. I have external and wish now that I had internal.
Confused yet ???
The newer technology is great but expensive, wish I could go that way someday. My LMS 520c's are very adequate, great color and screen and visuals no need to upgrade for my new boat, so I went with the Raymarine Auto Pilot instead.
Who will be boatless the end of next week waiting for my new ride, this will be the first Memorial Day weekend I didn't spend on the water, but I have plenty to do at home. Once the new boat comes in, I doubt I'll be home much.