I quite like the dual boot option personally, it's fairly easy to set up and doesn't suffer from slow down. I currently have win2k / slack 8.1 dual booting but two linux systems shouldn't be much different. And if your using GRUB dual booting is a snap. To add or edit your boot options you just modify the /boot/grub/menu.lst file to your liking, if you need an example, here is mine:
now if you were to do two linux systems you would just have to remove the win2k section and add a section similar to the slack section. You might not need the hdd=ide-scsi hdc=ide-scsi chunk, that's in there for my cd burner to work (emulating scsi for an ide drive).
color blue/black light-blue/black
title Slackware Linux 8.1
kernel (hd0,5)/boot/vmlinuz ro root=/dev/hda6 hdd=ide-scsi hdc=ide-scsi
title Windows 2000 Professional
Whichever method you choose, good luck and enjoy it!