to me maintenance is a small issue between a 14g and a 24. there will be minimal ammount of differnnce in time or difficulty of maintenance tasks.....slightly larger water change, little more glass to scrape etc....
what I would look into is what you will want to keep and modifications are common to the all in one aquariums to meet certain needs. For example in my 12g aquapod I upgraded the return pump, removed the sponge and the filter media, added new fan for light hood, later removed hood for a halide, and covered overflows to make i skim better. So again I would take into cnsideration that it is nicer to have more room for stuff but also which tank has more issues or which may need to be modified to keep what you want.
But if you just want to get it goin and get some things in it go with the aquapod for room. 12g aquapod was my first tank (so LFS doesn't always give the best advice) and I loved it but it filled up to fast and I went out and bought another tank.
