Personally, I'd put it in the Si, but that's partly because of emissoins issues - unless you can find the stuff to convert it to OBD-I (not II) for the 95 chassis, you may have trouble getting an emissions sticker if your state looks at that kind of stuff (texas doesn't yet, but they're going to start in a couple of months.. ugh).
Besides.. the Si is lighter, and trust me, that B18A has a LOT more torque than the D16.
FWIW - there's 2 D16's and a B18A in my driveway right now
90 Integra LS 5 speed (one roommate's), 94 Civic EX auto (other roommate's), and my 96 Civic EX 5 speed. The 'teg runs away and hides from the 94, and stomps the crap out of my car off the line (I can stay with him in 2nd/3rd though). All that's been done to the 'teg, engine wise, is a high flow muffler and homemade ram air (I have an AEM CAI and high flow muffler on my car)
Besides.. the Si is lighter, and trust me, that B18A has a LOT more torque than the D16.
FWIW - there's 2 D16's and a B18A in my driveway right now