The 540 at $369 makes the Equinox 600 look like a CTX feature wise, lol. You will have to decide if the additional $280 for the 600 is worth it if you want to get in the water (and be able to drop it) plus ALL the missing features on the Vanquish 540 model compared to Equinox including: no recovery speed control, iron bias is ALWAYS on which can hurt with masked targets, locked into 5 tones with no tone break adjustments, notch is rudimentary and limted to a minimum of 2 TID (no single numbers can be notched), NO SINGLE FREQUENCY option, NO GROUND BALANCE (fixed - though Multi IQ does a pretty good job compensating for non-ideal GB, so that is what they are banking on), need a rain cover for the housing (what is this 2015? lol), and fun with AA rechargeables (whoopie).
I do like the stem design and wish it could be adapted to the Equinox plus the three coil options are also great (V8 DD 8X5, V10 DD 10x7, and V12 DD 12X9) and it would be a bonus if they were cross compatible with Equinox. Otherwise, great entry level detector but I think Simplex being waterproof and wireless might be a better bet even if it isn't multifrequency. If Nokta/Makro could make a waterproof and wireless $299 detector, not sure why ML failed to do that at least with the V440 at $279 and a waterproof V540 seemed like it should have been mandatory - they might have had a winner on their hands on the 440. The 340 is arguably even more basic than the GO FIND, it has Multi IQ but lacks basic functions like pinpoint and even the GO FIND has wireless connectivity. So I would probably go with GO FIND for super basic operation vs. the V340. 340 is almost LIKE why bother... Multi IQ is not worth it with all the other stuff (waterproof, pinpoint, ground balance, limited tones, single frequency) stripped away.
Overall, even after hearing the specs, I haven't changed my stance on this Vanquish line since I first caught wind of it...basically I can sum it up as, "Meh". I think ML just missed the boat features wise vs. Nokta/Makro though as far as the Garrett ACE series is concerend - well Garrett might be a little nervous and that really was who ML was going after.