Well, first things first, the S2 is a smaller camera in hand. Half the weight, it doesn't seem like that much of a difference, but dimensionally it is smaller.
And I had not noticed the green tinted viewfinder of the S2. The Canon P finder is cool toned, but very bright and clear. My P finder is brighter than my S2 finder. The RF patch though in the S2, warm toned is much more defined than the cooler P patch.
That said, I actually was fondling my cameras this weekend, the result was in fact that I am much more impressed with the P finder than I was before. Comparing my cameras, the P finder is bigger and brighter than the S2. Though the S2 patch is better defined, the brightness of the P finder more than makes up for it and makes its patch easy to see and use.
I think a lot of this has to do with the fact that the P is a 5 year younger design than the S2. When compared to my L1 and VT the S2's finder does shine. I do not have an SP or S3 (P contemporaries) to add to the comparison, but I suspect there is a difference largely to be seen in my next comparison. The entry and exit pupil of the P finder is clearly larger than that of the S2. While both finders have a 1:1 magnification, the P accommodates 35mm framelines due to the fact that the finder simply has more viewable area.
To this point, I do think using a 35mm lens with the S2 is possible, but the 35mm framelines in the P are clearly wider than the viewable full area through the S2 finder. If you want to be careful with your edge composition with an S2/35mm combo you will have to really be into your finder and really look out to the edges. You have to do the same with the P finder, but not to the same degree because the framelines are there and you can see beyond them with a little work.
What else can I offer Joe?