thanks for all the comments so far.
The reason I've considered the mac mini is due to my budget and also since I have existing pieces: I already have a fantastic Samsung Syncmaster 23" monitor hooked up to this old PC I'm typing on... and a good keyboard too
I also utilize a WD 1TB external hard drive on fire wire and may get a second as a backup - both utilized for photos (hmm.... tricky). Hence perhaps save money on upgrade costs.
I looked at the prices of upgrading the Mac Mini straight from the store to a larger hard drive and faster memory... and it's pricey!! O_o... ouch!
I think practically anything faster than a single core will be an upgrade for me, although I'm hoping the Core 2 Duo and Mac technologies will make it WAY more faster.
As mentioned, I'm not into gaming although some video might come into the mix. This will definitely be a Lightroom machine.
Edit: Just looked at the Macbook prices and specs and looks like the lower end Macbook pros utilize similar hardware as the Mac Mini (2 GB ram, Intel Core 2 Duo)... in which case if I'd want way more power, I'd need to save a ton of pennies as the 15" Macbook Pro is $$$$. LOL