I had started with a 4041 shuttle, put 50 hrs on it but didn't like the shuttle, so traded in & up to the 4047 HST. Had a HST prior, and will likely always go with HST. But like you, figured the extra HP was worth it!
The LS tractors are very good machines. Mine blew a headlight fuse early on, no biggie, and that's been it for 140+ hrs. Like I said I'm looking to upgrade to a cab, so that means I have to jump up to the XR series (tier 4) or look to another brand.
The ONLY complaint I really have about my LS is that I would like more loader lift height & dump clearance. This is likely not an issue for most people, but I have found enough times that for my work, I want more height. Also, in comparing different factory cabs, the new LS cab didn't impress me as much as some other brands.
But anyhow, that won't effect you since you're not looking for a cab.
Parking brake location: I didn't like it at first, but like anything, once you get used to it it's a non issue.
Seat: it doesn't fold up because it's a suspension seat, much better than one of those standard spring folding seats.
Brake to get off: nope, as long as the tractor isn't moving (pushing the HST pedals) you can get off without doing anything else. Otherwise, the seat safety switch will shut the tractor off if you're butt isn't in the seat while pushing the pedals.