Shoulder plane size?

[Jason Buresh]

I was going ask my wife for a woodriver shoulder plane for Christmas, but having not used one, I am curious to which size people find most useful.

I cut a lot of 3/4" joints such a rabbets, grooves, and dados. Thinking this may be useful to help square up joints? Or ate these designed mostly for tenon work?

Also, I am kind of dead set on the woodriver. I know you aren't supposed to buy a tool on looks but i really like the victorian styling of it. Plus the woodriver is in our price range.

Thanks!