I've not seen the PS2 version, but I warn you that the GBA Tetris Worlds is fundamentally broken - you can shuffle and slide to your hearts content once the block hits the bottom of the screen, so all sense of urgency or difficulty is gone. Definite try before buy tests needed. Quite apart from why anyone would spend that amount of cash when a second-hand GB (not even Color or Advance!) and GB Tetris will give you the best version ever.
Iain, is this the same version of the game that you mention? It sure seems like there would be an option to stick the tiles once they hit the bottom.
Here is a link to the PS2 version that I'm talking about: http://www.thq.com/tetrisworlds/features.asp
I've not seen the PS2 version of Worlds yet - my comment above comes from the almighty slagging the GBA version got, which didn't have the option. Its possible that they have added it for the PS2 release, which is why I recommended doing a rent (or wait for a review I suppose) first.
I'll back up the reviews on the GB version of "Tetris Worlds" - it's poo.
There's an older version of Tetris out for the PSX, you may want to grab it - should go for cheap. It's passable - it's got some extra modes I wasn't fond of, but it's better than some Tetris conversions.