I live in Grand Rapids, MI which isnt a hub for any one airline. However, there are many options and my company prefers Delta and United. I currently have about 60k "skypesos" and 3 additional delta flights already booked this year.

My dilemma is that I just got the Chase SP credit card which transfers points to United. I also hear that United is better for international award flights. When I do redeem my miles one day it will be with the intention of using them for international flights.So knowing that I will gain some type of loyalty with delta this year my questions are:

Should I continue to build on the loyalty i'll get with Delta and stick with them?
Should I swap over to United and never look back?
How valuable is it that Chase UR transfers to United and not Delta?
Do you have any general advice on MileagePlus vs. Skymiles?

Thank you

Chase UR transfer to United, but Amex MR transfer to Delta. That said, United's program is better than Delta's (in my opinion). You do have a decent # of Skypesos, so if you want to switch, get your Delta mileage to an award level (60K is round trip to Europe at low level, but if you would be traveling with an SO you'll need 120K), and then switch. Or get an Amex card with a nice sign up bonus and when you find a Delta award you want use the MR to top off the Delta account to what you need.

I don't see much difference unless you are a heavy biz traveller. Set a goal and diversify your earning power.

I will note that Delta generally treats their non-status passengers better than United does, so if you go the United route, it's a slightly rougher one in some regards.