I can give you a little first hand experience since I have 2 sets of wheels for my car and i've had experience with both now.
My winter set up are the all season Double spoke 98 style wheel, 17x7 all around the car. My summer wheels are the same staggered size as the e36 M3, 17x7.5 FR, 17x8.5 Rear(M-double spoke 68 styling), with Goodyear eagle RS-As 205 50 zr17s and Continental Sportcontact 225 45 zr17s up front and 245 40 zr17s in back, respectively.
The summer tires, which are heavier since they are wider, have unbeliavable grip. They are also high performance, not all all season so it makes a big dif there too. This wheel/tire combo reaches down and grabs the freakin road and won't let go.
The winter tires, however, are lighter and I can definately feel that the car seems ever so slighty more agile, which is good, although the wider summer tires make the steering a little more weighty which is another point for the wider tires. I am not sure, could be my imagination, but I could swear the car is a little quicker with the lighter winter tires.
I haven't changed wheel diameter, just width, but I hope this helps you.