I don't know what the current price difference is, but the
B2910's options are worth $1000 or so to me. If you plan to be using a mid-mower, be sure and compare prices using a
B7800 with the mid-PTO (it used to be an option; not sure if it is any more).
As far as the B2910s comfort items go...
I use the extendable arms frequently, and it saves on the back strain (the older I get the more I will enjoy that feature).
I use the
B2910's much-improved cruise control quite a bit while finish mowing, whereas I never used the speed-set device that my older
B2150 had (similar to the speed control on the
B7800). Note: In case you're not familar with the
B2910 cruise control, it is simply a hand control that you use to totally control the tractcor's forward movement in lieu of the foot pedal, similar to the way small garden tractors hydrostat hand controls are rigged. On the
B2910 you can't back up using the hand control, but you can start, stop, and change forward speeds totally with the hand control and leave it set at a comfortable pace as desired. This design helps overcome limitations imposed by having the hydrostat foot pedal on the same side as the brakes in case the operator needs to use differential braking.
I like the included tool box, as I keep the mid-mower pins and other handy items there.
I don't remember if the
B7800 has the ratcheting 3-point height adjustment, but that has come in handy on my
B2910 on several occasions.
POSITION CONTROL: When it comes to grading, I used a box blade on my old
B7100 (no position control) and my old
B2150 (w/position control) and there is a world of difference in the smoothness of the job. However, I ultimately found the best way to smooth out a new yard was to use a landscape rake in the full down position. With the landscape rake, I preferred to use it on my
B7100 and position control didn't matter. Mowing with a rotary was the only other task that I strongly prefer the position control.
I don't use the tilt steering wheel nor the telescoping wheel very much at all, though the arm rests are comfortable.
I'm sure that you'll be happy with the
B7800. If you ever did regret not getting a
B2910, it would probably be several years down the road.
Good luck, not matter which choice you make!
Kelvin