Sorry to hear about your rollover - I'll bet that was not fun. Hopefully did not damage anything other than maybe your ego a little /forums/images/graemlins/grin.gif
The rollover situation you described could affect any tractors stability as well. If I were you, I would try to mow up and down the hills until you find out where all those "rough" spots are and then you can use your new FEL to fill them in.
I can't really comment on comparitive stability between the two, but I can tell you I use my TN VERY carefully on my property as it is steep in certain areas. I prefer to go up and down rather than across the hills due to my comfort level.
I recently purchased(within the last month) an Acreease mower also, so I can use it to cut the steeper unexplored areas of my property. I'm using an ATV to pull it though so I can jump if necessary /forums/images/graemlins/grin.gif and rollover lessons on an ATV are usaully easier on the pocket. Actually my 6'3" / 260lbs is pretty effective counter weight on my ATV - but not so on my TN.
Set the tires to widest settings on either one you choose and always keep any front or rear attachments as low as possible when working on slopes. Also, do yourself a favor and actually check the steepness of your slopes and explore any additional obstacles and opportunities BEFORE you use your tractor - and remember keep the rubber side down /forums/images/graemlins/grin.gif
Regarding the cab - I don't think the weight will make too much difference either, unless you hang too many pairs of fuzzy dice from your rear view mirror /forums/images/graemlins/grin.gif