• ARQ discards "bad" packets, while FEC uses all of the received energy to produce a (hopefully) error-free packet.
• As long as ARQ retransmissions are rare, the loss is minimal.  Rule of thumb: no more that 1% packet loss rate.
• We are far worse than this on most amateur links!
• Small packets may help, but adds considerable overhead.
• The alternative (increasing power and/or antenna gain) is not always practical or economical.
• Brains over brawn!