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