I was using an i7 PC set up with 8gbs of RAM and i was pushing it with my productions on some occasions.
I recently upgraded my memory to 16gbs and i find it helps a lot.
I had a macbook pro too for producing on the go or at work during my break but i ended up not really using it, for me i preferred my studio PC and big monitor etc, it just works for my work flow and eventually sold my Macbook pro.
If you maintain your PC and have a good file system and drive speeds for your files then i think your ok with an i7 16gb PC.
but if your into live performing and all that then your prob best off switching to the mac for the performance reliability....at the end f the day its different strokes for different folks.