I've had three Triumphs in the past four years, left to right in this order...
The Speedmaster was first in 2003 and I never felt comfortable with the feet forward controls. The laid back riding style put more pressure on my lower back, also.
The Sprint had a forward-leaning riding position, which was great for controlling the bike, but was too severe for my knees which would cramp up after about 2 hours. My lower back was fine, however.
The Bonneville is my current ride and it is my favorite. I'm actually able to take longer rides on the Bonnie than the other two because my knees don't cramp and my lower back doesn't ache. Handling is surprisingly close to the Sprint and I really like having the pegs directly under me, i.e. a standard riding position. The windshield on the Speedmaster made high-speed highway riding much easier because I didn't have to grip the handlebars too hard. So for long distance touring on a Bonnie, I'd recommend a windshield.
Naturally, everybody's body is different, so you'll have to make the choice.