From my observations floating calipers which my 99 ML has are pretty weak as brake calipers go. They are however, just fine for a street car. I have no complaints about my ML's brake system. The floating calipers on my vehicle have but one piston per caliper. Brakes on high performance vehicles have at least 4 pistons per caliper and many have 6 or 8 pistons per caliper. I don't think the floating calipers are very rigid and I would not think they would be very precise in applying clamping force equally on each side of the brake rotor.

I would think your 98 has floating caliper too. As far as any difference in doing a brake job I would say no since most all brake calipers have one pad on each side of each rotor that needs to be changed and one or more pistons that need to be pushed back in.