Each has it's advantages:

Size of particle captured: Advantage Stainless
Flow rate: Advantage Stainless
Ease of use: Advantage Paper
Potential for Error: Advantage Paper (You have to service the stainless models--what if you don't clean it well?  The paper filter is 100% clean every time.)
Economy: It's a draw (IMHO) **Update, Advantage Paper (see below)

Paper is $22 per change -- about 6.5 oil changes until you break even. 

**UPDATE: HiFlo now makes cheaper (and supposedly better) aftermarket oil filters to fit 2012+ 690's.  Available on Amazon for about $13 with free shipping.

Our service schedule:

Once after 1,000 km (621.4 mi)
Every 10,000 km (6,214 mi) or annually or after every sporting use.

So really it comes down to how often you intend to change your oil.  If you're racing hare scrambles every weekend, it might be economical for you (but I have to wonder why you didn't buy an EXC). 

I'm gonna stick with the disposables.  I'll probably change the oil every 2k miles or so, 3x more conservative than the manual suggests, and I still don't think the economics of the stainless models win out--even at the KTM stick-it-to-'em price of $22.  The price for paper filters will come down as soon as K&N gets around to making one for the 2014. 

But mostly I'm lazy.  I don't want one more process to prolong the oil change.  Plus, it's a grimy process.  My wife would not take kindly to my ruining her Tuperware by soaking stainless filters.

Besides, for $130 you could treat yourself to a set of rally pegs, and wouldn't that be more awesome?

I've never used the stainless filters so I can't speak from experience. I've read somewhere that the paper still filter better (again I can neither confirm nor deny from experience) and I know of one guy personally who used one and switched back to the paper. I will say you don't buy a KTM to be frugal, lets face it your going to pay a couple thousand dollars more all day every day over the Jap. bikes. But you get a performance bread, no compromise bike. Also the 690 had FOUR oil filters in it, so while the oil changes can take longer, these motors seem to be very well protected. I only have 1,700 miles on mine so far so again time will tell. But so far I love this bike.

My wife would not take kindly to my ruining her Tuperware by soaking stainless filters.

Easy solution    Do it when she is not home.