They're the same GPU (both are GCN with same core count, TMU count, and ROP). Same price, very similar coolers, if not identical. The difference is OC. The 270X has a 30MHz disadvantage in core clock, but has a 200MHz (800MHz effective) advantage in memory clocks. Personally, I'm leaning towards the 270X, plus it looks better.
The 270X is a 7870, the one I linked is $50 cheaper than your cards after the MIR and should overclock better. Tiger Direct almost never has better prices than Newegg, Amazon and NCIX in Canada.
Just remember that the 270x (like the 7870) has 2GB/256 bit so if you are using/planning to use multi-monitor setup, you will be hard pressed. Other than that, I believe that the 2GB/256 bit combo will do okay in most of the current titles.