I like the Ruger it is a well built gun. They are just plain but ugly IMHO. I find them to be too bulky.
The P220 is a world class 45. It is one of the most accurate out of the box production guns on the market. The trigger on a P220 is superior. DA is smoother and the SA will be crisp. I really find the SA trigger on Sigs to be magic. Closest thing to 1911's or BHPs that you can find in DA/SA gun. They are very reliable and have great feel in the hand. They point very naturally for me.
The resale value on a Sig is much better. If you buy one today for $500 you can sell it tomorrow for $500. The Ruger will cost you $400 or so and if you want to sell it you will be luck to get $300.
To me they are just a different class of weapons. The SIG is superior. For a difference or about $100 to me it is a no brainer.