Well, a Commander 114 is in a different league performance wise to a TB10
The TB GT range has about 2" to 3" more headroom, due to the curved composite roof. This obviously slowed them down a little so Socata did some cleanups to avoid having to change the performance data in the flight manual
On the TB20/21 they made the footsteps retractable and changed the wingtips and some other details.
As I said, if the man can stretch to a TB20 he will get a whole different class of plane. The range is about 2x better (1300nm on economy cruise, to zero fuel), it's a lot faster, same MPG, climbs at +1000fpm at max weight, 20k ceiling (enough to get above just about all stratus cloud).
I spent some time in 2001/02 looking at TB10s but all the ones I found were quite old and in less than great condition. No GTs. This was probably because European sales were poor after the 1980s, due to excessive pricing and the plentiful availability of cheap PA28 type wreckage which "does the job".