What would be the biggest difference between the 9 and 10 maintenance costs if there are not many miles being put on the car? I don't drive a lot and I've seen the major things to look out for, but anyone have any specific pros/cons they've encountered with one or the other?

 

Hello & welcome aboard

The EvO 10 & the 8 & 9 will have a similar maintenance table profile.

Now, the 8 & 9's may have more average miles (being older) so the maintenance level is higher, which is a bit more costly

 

I think the Evo X's has timing chain, so you don't need to worry about timing belts. But, depending on year, the older X's have chains that can stretch. Also, the trunk has struts that will eventually need replacing.
If modifying for power, I think the iron block in 8/9's are more forgiving than the aluminum blocks in X's.

 

if you live in salty area your ACD pump on the X is likely to go. i don't think the belts are a big deal, just one thing relatively minor thing when you get the 30/60/90 water pump etc. otherwise i think pretty much the same