For a given pad, it's all about mechanical advantage (lever length). You have two fundamental givens, the brake bridge location and the wheel diameter. This combination determines the distance between the pivot point and the braking surface. No mater which caliper/lever configuration you use, this remains fixed for a given wheel (27" or 700C). the distance can be altered by using an offset brake bolt, but now you have included an additional moment arm in the system equation as you have two "anchor" points for the caliper. The question is which is going to flex, impacting performance, the caliper moment arm or the offset bolt. Likely not the latter. Is this why people like to use them as they can use a caliper with a shorter reach?

What are the remaining variables to consider?

Spring rate (does not need to include how long or short the engagement point is), the distance from the cable to the pivot, as discussed, and the lever moment arm. So given the lever arm distance is fixed you have two variables left to compare between the calipers, the distance from the cable to the pivot and the spring rate. The spring rate should not really be a factor as you can overcome the spring regardless of the rate. I doubt the difference would impact your perception of braking capability vs. actuation performance. Some brakes systems are hard to use but work very well, just difficult to modulate!

So between the two calipers, is there a difference in the distance between the cable and the pivot point? If yes, the longer distance should give you better braking capability.