glenridgerich,
Would kind of depend on your budget. $2400 more for the T120 gives you 80 hp instead of 55hp for the T100, if that is important to you.
Either way, I think Triumph makes pretty sophisticated and reliable bikes. I had a 2012 Tiger 800 XC that I rode for 27,000 miles before trading on a 2015 Tiger 800 XRx that has about 20,000 miles at the moment. No trouble with either one. I traded for the street version XRx because virtually all my miles on the XC were on pavement plus the XRx has traction control, ride by wire, rider modes, cruise control and even self canceling turn signals. I added heated grips and TPMS. Both had ABS.
Service is kind of pricey, although very thorough. I figured at least 10 cents per mile. Might want to check into those costs.
I found the Bonneville to be kind of cramped and it seemed I couldn't put my feet down without the pegs getting in the way. I preferred the Thruxton with the rear set pegs and was about to buy an Ace Cafe edition in 2015 when the Honda dealer offered me the CB1100 ABS for $3000 off MSRP.
Good luck with your decision