Taken from the handy-dandy BBM bike info spreadsheet: http://spreadsheets.google.com/pub?key=rU4QBnyJGHjHiCQAtii4KeQ&single=true&gid=0&output=html
Ducati Monster 696, 696cc, 2 cyl, L-twin, 78.8 hp, 50.6 lb-ft, 355 lbs
Triumph Thruxton, 865cc, 2 cyl, parallel, 69 hp, 52 lb-ft, 451 lbs
Monster power/weight: 0.222 hp/lb, Monster torque/weight: 0.143 lb-ft/lbs
Thruxton power/weight: 0.152 hp/lb, Thruxton torque/weight: 0.115 lb-ft/lbs
As you can see, the Monster has substantially more raw HP and a much higher power/weight ratio thanks to its 100lbs-lighter weight. It is also relatively “torquey-er,” again thanks to having the same torque figures but less weight. The main issue for a beginner with the Triumphs will probably be that extra 100 lbs. I haven’t ridden either the Monster or the Triumphs, so I can’t comment on their handling character, nor do I know where in the rev range each bike makes most of its power/torque. I have heard that the Monster line tends to have pretty grabby throttle response, however, though the same could be true of the Thruxton for all I know.