I've had good results with all the maltsters I've used. Off the top of my head I know I've used Crisp, Breiss, Weyermann, and Rahr recently. Rahr 2RP at my LHBS is like $40 a bag with our club discount, the Crisp MO I think goes about $60.
Let's say you're making average beers (1.040 - 1.060) and you use about 15 - 20 LBS per 10 gallon batch. You'll get three batches from a bag of malt so your cost difference between the domestic 2RP and the English MO is about $8 per batch. Not a deal breaker but worth considering. You will get more authentic (to style) results for your English beers using MO, but it's up to you whether or not that's important. You may find you just like the flavor of one maltster over another. There will be differences, sometimes huge, in the flavor of the grains based on growing conditions, protein content, the terroir of the growing area etc etc.