Your instincts are right on: the steering response would be a little quicker on the Lexa. How noticeable 5mm is depends somewhat on how much weight you have towards teh front end of the bike. In normal road riding you might not notice it at all…in a crit race I imagine you would.
-If you plan to take either of these bikes and add clip-on aerobars and/or a forward-offset seatpost to achieve a more forward & low tri position I’d lean towards the 2.1. Two reasons: more trail means more stable as you get more weight out front, and the lower stack height makes it easier to get lower without resorting to oddball stems.
-If you are going to just ride the bike as-is for multisport racing and training I might opt for the Lexa as the more versatile platform of the two.
In either case, if speed for the same amount of effort is important, spend the next $ on a fit and/or cockpit changes/upgrades so you can comfortably stay in the armpads or the drops for the duration of the race. If you’re there already, then an aero helmet, and finally an aero wheelset.