Subs require more of their people as there is still much to be done but with a much smaller crew. It is hard to pigeon hole someone on the boats to one job area. For example an ELT on a carrier may be relegated to doing just chemistry (primary or secondary) on watch but on the boat you will be standing watch in the engineering spaces and doing primary chemistry, secondary chemistry and any radiological work in addition on your duty days. Another downside is that on the boats you may be assigned to messcooking while you are doing your Basic Engineering Quals and Sub Quals (most are not).
I would still go for a SSN, both of my boats were attack boats, though the SSGNs sound interesting to me as well.
As far as getting an education while in, a carrier would be a better choice you would have more personal time.