They are pretty interchangeable for the process that you'd use for your partial mash, but they will contribute some different flavors. The domestic 2 row will be lighter and a bit more neutral, contributing less to the flavor. The Maris Otter (British malt) will add a slightly bready/toasty quality to the beer and tends to make the beer have a slightly thicker mouthfeel. It'll also likely cost more.
Currently On Draft: Bamberger Rauch Dunkel, Belgian Blond, Pilsener Urquell clone, Smoked Porter
Bottled: Concord Pyment, Mi'Apa Sparkling Mead, Chimay Blue, Old Simcoe American Barleywine, Old Cantankerous
Fermenting and Conditioning: Pseudo-Decoction Munich Dunkel, Left Hook Bitter
Recently Kicked Kegs: Fresh Hop Pale Ale, Citra Rye IPA
On Deck: Old Rasputin, Northstar IPA, Ur-bock Dunkel