Firstly, pneumatics are considerably cheaper than cordless, not to mention smaller, lighter, etc, but as you have Makitas already you'll probably want to take a look at the DBN500 (18g) - a peculiar looking gun, very expensive and large and I personally found unwieldy for an 18g nailer (I tried one a while back when we had glaziers on a job who were using them - they had them only because the firm had standardised on Makita LXT batteries for the cordless kit). Frankly I prefer even a Paslode 2nd fix gun to this, despite generally detesting gas guns. The next size up, the 16g
DBN600 is similarly expensive and heavy, although more conventionally styled. but I wouldn't recommend that, either, having tried (and failed) to get one to sink 50mm pins into hardwood (American oak) during a dealer demo day. Both these tools are air over battery (i.e. they see battery power to compress air which in turn is used to drive the pin into the wood), so you'd have thought that on a prof4ssional tool they'd be able to sink 45 to 50mm nails into hardwood. The only other pinners sold by Makita are the little 23g DST221, etc models which are designed for tracking beading, etc on place. Again a "dear do" and with a lot of negative feelings expressed on the net (never used one, so can't say personally). TBH whilst Makita do a lot of things well (and maybe I'm a "fanboi"), I'm afraid that nailers aren't their forte IMHO
But then the same could be said of Milwaukee 's first generation 2nd fix nailers (15, 16 and 18g), all of which have fallen well short of the mark (they tend to lock out if driven at any speed, or bump fired for more than 10 or 12 nails) - so much so that they have embarked on a "Gen 2" (ground up redesign) range which will start to appear in the USA from October (?) 2019 onwards. They look interesting
I reckon that the best bet for cordless 2nd fix is currently the Hitachi 18 volt stuff. Again air over battery, these guns
will sink 50mm pins in hardwood (15, 16 and 18g - tried them all). Hitachi also make a first fix gun which is comparable to the DW cordless in performance.
To put this in perspctive, I currently use a DW 2nd generation 1st fix gun (DCN692 - the better 2-speed model) and 2nd generation 16g gun (DCN660). The DCN660 can't sink 50mm pins in some hardwoods which means that DW won't be selling me an 18g gun. This is despite having had success with their 1st generation guns (16g and 8g). So I, too , am looking at the market and at the moment Hitachi is the front runner for me, despite having a non-Makita battery