PokerTracker

I was just wondering peoples opinions regarding performance (or maybe another reason as well?)
Would it be better to have
- 1 Database of 3 Million hands
or
- 4 databases of 750k hands

Assuming in both cases they were both (and all) clustered/vacuumed/analysed/cached
and while playing I'm importing into another separate database.
Also the main use would be for hud rather than going through and looking at hands.

Personally I'd go with 1x3M. But much more than that and I'd start a new database. 5x3M is better, in my experience, than 1x15M -- if for no other reason than the housekeeping time gets quite long then.

If a database has had a full housekeeping done to it, does it make any difference how many hands are in it performance wise when using hud?

It shouldn't.