I have a chance to trade my MBA 11inch 64hd for a brand new mac mini.Would you go for that deal?
You're kind of comparing apples to oranges, one is a portable, the other isn't. I don't know how you use your MBA so I can't say, that is sort of a personal preference. For example, although it may work for you, I never would have bought an MBA as my main computer as it wouldn't suit my needs for a number of reasons.
If the MBA always sits in the same spot on a desk and you never use it in front of the TV etc or take it out of the house to use elsewhere you really don't need something portable.
You'll also need a monitor, keyboard and mouse with the Mini. The Mini can hold more RAM, the processor is faster, has a bigger HD although not an SSD, and has more ports.
But again it's not portable. Only you can judge if you need/want the portability.