If you plan on cutting through brush, tall weeds, and saplings, just make sure it is the brush cutter (rough cut) and not the brush mower. The mower does much better on tall grass, (mowing food plots), but is not recommended for brush/saplings (and you will experience breakage if you use it for that). The brush cutter will eat up the heaviest brush and saplings, but doesn't like tall grass (doesn't cut it cleanly because of the big heavy blades).
One advantage to the 44" 14.5 HP version over the 12.5 HP version is electric start (but that also requires a battery). The 12.5 HP is pull-start. I have the pull start and don't find it to be a big problem.
If you want to drop another thousand over the 44" 12.5 HP, you can get the 52" 18.5 HP version. Besides size, a big advantage of the 52" version is it a 4-wheeled mower. I've often found the 2-wheeled version is difficult to level, and either you have the front-end too low or the back-end too low (and adjusting the height is kind of a pain). With 4 wheels, it is much easier to adjust the height and keep it there.
We have the 44" rough-cut trail cutter and love it. We used the snot out of it and no problems. But again, it doesn't like cutting tall grass like Johnson grass or heavy foxtail. The big blades are made for smashing through saplings and head-high briars, and it does that with ease, even saplings as thick as broom-handles.