If you go with a trunk bag, you'd have the hose running up your back of course, and there wouldn't be much for it to get snagged on, but dealing with the bottle itself would require you to dismount, and dismounting while managing the hose would be a little tricky.
If you go with a front rack, you'd have the bottle close at hand, and mounting and dismounting would be simpler, but there's a lot more stuff for your hose to get snagged on while you're riding.