David,
I have the corded Makita. I haven't looked, so I can't speak to power, etc, but my drive towards cordless tools is based simply on two tests.
First, how often do I use them. And the secondly, how often do I move them from location to location. For me, I break down my plywood in the same place in my driveway every time and I don't it all that often. I also don't go out to job sites or use the track saw in multiple places in the same work session or closely in time in different places.
So while I bought my track saw corded, if I was making the decision again today, I would buy another corded one.
Things like drills, impacts, sawzall, etc that I tend to use all over the place and often I definitely go cordless as it just saves a lot of time and trouble having to lay out extension cords all the time.
Battery technology is much better, so I have essentially stopped worrying too much about strict rotation of different batteries to prevent one self-discharging and ruining itself. Additionally, their capacity tends to be long enough that you don't get a lot of those annoying stops right in the middle of a cut. So I don't think I'd be afraid of buying the cordless one.
But why pay more if you are not going to actually consume the primary benefit of a cordless unit which is mobility.
FYI, if you are buying the saw and want to get additional track, home depot has the 55" track cheaper on-line than in the store (at least a month ago), so show the check out clerk the online price so you get the lower price. The HD online price with tax is right in the range of ordering online and you can easily check the track for straight ness and return it if necessary.
I've had 4 of the Makita 55" tracks (two got damaged during use over the last few years) and actually bought 6 total as 1 had a real unacceptable bend and 1 more had a bend that was just right on what I would consider acceptable for breaking down materials, but the store is 5 minutes from me and had a stack of them, so I just took it back for a new one.
Mike
(edited to replace sawmill with sawzall, I don't have a sawmill, but if I did, I doubt it would be cordless.)