I personally would have been fine with either trans type. However, at least in the 25 series, if you want a cab, you get HST. That's it. Mandatory choice. My personal requirements included a mandatory cab, (which again, in the 25 series, comes with heat and a/c standard). Not the same for others, I understand, but for me, it was cab or "h*ll no". So I got the HST.
I have a couple of steep sections of my road ditches that I mow that are over a 22 degree (that's "degree", not "percent grade"-it would be a 44 percent "grade") slope. I mow with a 6' rotary mower, and for the steep parts, I mow it driving straight up and straight down the slope. When I get to the steep portions, I mow straight up in HST 1 (low) range. The rest of the time, I'm in HST 2 (middle) range. I easily mow up the steepest parts in HST 1 range, with the front axle engaged, diff lock on (if the ground is soft), and mow at full rpms all the way up the slope.
So I mow along the bottom "flat" area, and as I make the turn to go up the slope, I shift to HST 1, mow up the slope, get to the top, make the turn, and shift back to HST 2 to continue along the top. Then I just rinse and repeat same as I come around for the next pass until the mowing is done. Only time I have to shift into HST 1 range is at the very steepest sections I mow. Rest of my mowing is all done in HST 2. I have no complaints.
I wouldn't squabble about "losing" 5 hp for an HST trans over a gear trans. If 5 hp is the difference between getting the job done or not, you probably bought too small (hp) a tractor anyway. Some other tractor brands lose more hp in their HST designs. But the Branson, with only a 5 hp drop, is the most efficient HST design (as far as power loss) that I've seen. I wouldn't lose any sleep over it.
And for some reason, only the cabbed version (at least on the 25 series), the diff lock is under your left boot heel, not your right. Don't know why it's different, but it's too bad the open station tractors have the diff lock on the right side of the floor pan. I hope they do change that in the future.