I don't know if there is any real difference between a mark 1 and a mark 2. I thought it was just the picture on the front of the finder.
I've never used a mark 3 so not really able to comment personally but I know people sold there mark 1&2 finders for mark 3s then wanted there old finders back.
Personally I like the old finders maybe it's just because it was what I learnt to ferret with and I don't like change. I'd be interested to see what people think.