Toro Sr4 Super Recycler Lawn Mower - model 20092 w/Briggs & Stratton Engine vs. model 20099 w/Kohler Engine?

I am looking at buying a good rear self-propelled lawn mower. I have been looking at the Toro Sr4 Super Recycler Lawn Mower model #20092 with Briggs & Stratton Engine vs. Toro Model #20099 with Kohler Engine. Which one is better or what rear self-propelled lawn mower would you suggest for 1/3 of an acre of mowing and I need a good mower as I have some disabilities. Thanks JM