i agree. box turtles are easier then RES.
the minimum size area needed for one adult boxie is a 4X4 pen. Chris is right when he says that the glass can stress them out. if they see a way out, they could claw at the glass constantly.
i keep Carolina in a rubbermaid container. since i live in FL, and i'm in an apartment with chill roommates and a big balcony i put Carolina's container outside. she's loving it, you can tell! she doesnt hide has much, and i caught her streching out her neck to catch the sun's rays. So outdoor areas are ideal.
the only problem i have with boxies is that they are very very picky eaters. they can be eating fine on one food, then completely turn their noses up at it and never eat it again. variety is key.
also, beware if you buy an adult boxie in a petstore. they are wild, and stressed and will have problems when you take them home. boxies have a homing chip in their heads, and if they are taken too far from home they become disoriented and stress a lot easier. if you can get a captive bred hatchling from a breeder, do so. it may cost a lot of money (i dont know, mine was free!) but it is totally worth it. think of it as an investment.
also know that boxies can take up to four years to become full grown. so if you get a freshly hatched baby it will stay small for a while. i'm not condoning a 10g tank, but a 20 should be fine for the first few years.
here is Carolina's container when i first got her. i have two hides now, a better soaking dish and no food dish, she just gets fed on the concrete stone and i planted organic grass in it which she loves to burrow in. the plants are still there, just skewed around more.