They both bring something different to the table. As you say Sidebottom adds hardness but Hartlett is a bit classier and creative by hand and foot. Both are capable of winning contested footy and both are capable of going forward and kicking goals. Right now you'd have to say Hartlett has the runs on the board since u16's and would be the conservative pick. However it's also easy to forget that Sidebottom is bottom aged and has 12 months of development up his sleeve. I'm a big fan of the way Sidebottom approaches the game with a combination of footy smarts, confidence and hardness, but I'd probably have Hartlett just in front now. Just my opinion though, others may differ.
I wouldn't be upset to see either in navy blue.
Edit: I've had a frustrating couple of years following the TAC, my personal favourites seem to be around about but just outside our pick
The reason Sidebottom interests me is that the hammering Judd copped in the contested footy, we could really do with a Bartel,Mitchell,Lewis,Hayes type.
Could you compare Sidebottom to Bartel & Hartlett to Gibbs.
If so I'd rather Sidebottom.