He can also use a zorro adapter for the side slot and use anything from RTG boards to a Deneb.
Good luck plugging a Deneb into a slingshot adapter...

No, seriously: if hardware is already present a 500 can be a nice machine. But I'd take a 1200 any day when it comes to using and upgrading the system.
- adding an HDD is peanuts (simple IDE vs. external SCSI controller + disk)
- adding a CDROM is easier/cheaper
- adding RAM is much cheaper
- no need to add a cheap accelerator, '020 inside
- no need for 2 MB chip RAM upgrade
- no need to upgrade Agnus/Denise to get VGAish video - a simple alternative to RTG
- no / less clunky external expansions