Hi Ku,
The reason why one might want a player rather than a recorder/player is that, according to some, a player tends to be more sturdy and robust than a recorder/player. Here's a quote from famed MD Repairman, David Popovits taken from http://www.minidisc.org/repair_info.html
"Buy the right MD. If possible, buy a portable player. Those tend to have less problems than recorders. Do your recordings on a MD deck, It's easier. If you cannot have 2 MD's as stated above buy a recorder that is known to be strong as possible. Try those having hard metal covers (MZ-R90/50) and those that are not known to have recording problems. You may refer to opinions brought by members of the MD Community Page."
I, myself, have two MD units. I keep my MD recorder at home and take my more compact player with me when going out.
Best regards,
Postpositivist