Kardon:The ps3 processes the work units much faster than a normal pc. It may take a few days for your pc to finish a single work unit were as your ps3 probably does a few a day. If you are folding on a slow machine or you do not leave your computer running 24/7 you may want to select the option to only accept work units without a deadline. From what I understand work units sent in after the deadline earn no points.
The PS3 workunits are totally different and have been sized for their target audience.. People don't run a PS3 all day long like they do their PC and so the workunits are smaller and meant to be completed within hours.. The SMP client for multi-core CPUs has much larger workunits and the reward is greater.. Indeed a quad-core Q6600 can do more science than the PS3 can. But a dedicated Q6600 build is going to be more costly.. You really do get what you pay for in the end..
If you're going to game, then go ahead and get a great graphics card to run folding@home on in the meantime. If it's a dedicated folding box, then'll likely be better loading up with quad-cores.
Also, as far as I know, the deadline less workunits have been unavailable for years. If you enable it, you will get no workunits. It's going to be removed from the next console client (I think it's already gone from the Beta).