The Cliq has a neat looking interface optimized for social networking called Blur. It does appear to lack of the Google apps though.
The MyTouch3G is more of a true Google phone than a modded Android. You got more of the Google goodness on it, plus it can currently be updated to Android 1.6. This has a number of improvements over 1.5, including a better Android Market.
My personal and subjective opinion is to stick to the MyTouch3G.