V3 is the best IMO, down side is battery contacts on the bottom plate after a bit will collapse some. So far though I just bend them back up and that works but over time I do see they may wear out.
Performance it's a beast along with long battery life and more wiggle room with the additional amps. For me good ergonomics and comfortable.
V4 is a piece of shit. I was looking forward to the 2x700 batteries and pre-order one. The spring for the switch is obscenely tense, very uncomfortable. That and the switch assembly is press fitted in, absolutely unsat for a Mech, bad design. Also it has a tendency to chew up your battery wraps even after the first use.
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