which to buy 40gb vs 60gb CFW compatiblity

Hello I am looking to buy 3.55 firmware console, it's between the cheaper 40gb model and more expensive 60gb. I'm wondering whether there is any major difference between the two models or even other models in terms of how exploitable the console is. I know that 60gb can play ps2 games on disc (I have a modded ps2 anyway) is that the only difference ? Obviously the 20gb difference but I have a external hard drive and I could upgrade the internal memory.

So do you think I should get the 40gb?