First of all: the sets only work for 0..255 (at least in current fpc afaik).
The question of speed can actually not be answered.
That depends on the compiler and options.
It might be that current FPC compiles "Solution A" to faster code, but that the next release will make "Solution A" the slower option.
Same for the speed could go towards either one, depending on compiler options, optimization level, or even for which CPU you compile.
To make it all even better. If you compile the 2 solutions once, with the same fpc, the same settings, for the same cpu, identical....
It could still be that on an Core-I5 computes "Solution A" faster, and a Core-I9 computes "Solution B" faster.