Also with a Canon 450d in the house it seems better to go for a Canon as we can share lenses.
That sounds like another good reason to go for the Canon.
Certainly save you money in the short term, allowing you to borrow a lens or two to try, then buy your own later.
(And if they ever upgrade, you might get first dibs on it)
I have a lens on (permanent) loan from my Dad because his Minolta stuff fits my Sony.
I did just get a load of filters off him too.
