"which would you say is the better product?"
It all depends on what your uses are.
Personally I would say the HP is the better, based on what the HP has on it/with it, the HP has 4 GB DDR2 memory (whereas the Aldi one doesn't mention what memory type it has apart from that it has 3GB, the Vista 32 Bit will only show at maximum 4GB, minus any graphics card memory, for example, if you have a 512MB graphics card, then Vista would show that you have 3.5GB, this is what happens on my PC which has 4GB of ram and a 512MB graphics card)
Also th HP one seems to have a lot more with it, and also seems to have a better warranty (1 year, pick-up and return, parts and labour
A +2 years warranty extension is available - HP Care Pack U4819E or
U4821E (including Accidental Damage Protection) Express service
UE601E (D+2 Turn around Time)
I'm not sure of which will have the more power fuller processor, but someone on here will probably help you on this.