It's better because if someone gives away your public email address to spammers, one of two things will be true:
(a) you know who did it and have the ability to block it, because spam comes to the address with the offender's unique tag, or
(b) the spam is automatically sent to the trash and you never see it, because it goes to the base email address.
Personally I only use one email account, but none of these setups is very hard to effect. It really depends how much of a problem spam is for you. With Gmail's excellent spam filtering, it isn't much of one for me, but the +tags can act as a second line of defense.