With single effects, your sound has a lot of versatility. You can arrange/rearrange effects and sculpt your tone very precisely with easy-to-use knobs. On the down side, most single effects pedals are not programmable for different degrees of sound. The effect is either on or off. If I need to change sounds between songs,I have to bend over and twist the knobs.
I currrently use an Ibanez TS9 reissue and a Danelectro Chorus and Delay. I am thinking of trying one of the new generation of multi-effect pedals, such as the Korg AX-1000 or Boss GT-3. These units are very versatile and I have been very impressed with the sounds from the GT-3. You must spend some time with any multi-effect unit though - they are considerably more difficult to program even though you can get superb sounds.
[This message has been edited by Jon68 (edited 08-18-2000).]