Better to have 2.5gb mismatched memory or 2gb matched?

I currently have a mid-2007 macbook with the standard two 512gb memory chips installed. I'd like to upgrade, but I don't know if it would be better to buy one 2gb chip and mismatch it with one remaining 512gb chip (2.5gb total) or to replace both chips with a matched pair of 1gb chips (2gb total). Thanks in advance for your help!

It is said that it's "better" to have two chips of identical sizes to take advantage of that whole dual-channel thing, but I have one 2gig in one slot, and one 1gig in the other and haven't noticed any ill effects. It acts like a machine with 3gig should, i.e. faster than one with 2. If you're going to go with mismatched RAM chips and you have a Macbook that only takes the 3gig like mine does, you're better off going with the max and putting the 512MB chips in a closet.

Though I had the situation where I needed to max out TWO macbooks of the same vintage, so by getting a 4gig upgrade kit I was able to make them each 3 gig to max out the RAM. They are both just fine.

I dont know the answer to 2.5 or 2 gb, but what i would recommend is to get a 2gb memory now (so to have 2.5) and then in the future when you save up a little more get the other 2gb memory so to get all the way to 4gigs.

If its really a mid 2007 macbook then the max ram is 3GB. So get the 2gb memory now and you could always get a 1GB to have it maxed out in the future.

PS: i think there's no such thing as dual-channel in Mac.