Cold War Gone Hot/Red Storm Rising

So recently I've been looking at the blog Small Scale Operations, which is currently running a massive 'what if' game where the Warsaw Pact attacks NATO in a conventional (non-nuclear) war. Which is also the basic plot of the book 'Red Storm Rising', by Tom Clancy. Which I just happen to be reading (again).

 Some of the NATO ground forces from Small Scale Operations

So the inspiration's there and I would love to do a Cold War Gone Hot project, but there are some considerations that need to be taken into account:

1)affordability.

I cannot afford to be shelling out hundreds of pounds for models which I may not use for ages.

2)storage

I am running out of shelf space, and don't have a gaming room.

3) rules

I have no idea on rules either, so I need help picking a rules set

4) I am also wanting to do other projects, such as working on my 28mm nappys, which won't require buying new models.

This has lead me to a decision. I have two scales I could use for this project: 20mm, like Small Scale Operations is doing, or go down to 6mm, using Skytrex 1/300 tanks. Both present challenges as to what to buy, because although I already have lots of generic European terrain, such as hills and trees, in 20mm scale, I've never done anything in 6mm scale before. However, in 6mm scale one can use paper buildings and the like, and trees should be easy to make. So I'm stuck on my decision, 6mm or 20mm. I've set up a poll on the left hand side of the blog, and hopefully it will attract more votes than the last one.