Aspiring 14060M owner just saying hi!

[Intheshed]

Hi,
My first post here so go easy please!
I have wanted a Submariner forever and, having now researched them to death, I know that I'm in the market for a 14060M. I love the clean lines and the fact that I can put it on a NATO strap. What I can't figure out (despite the hours spent on-line) is whether to go for the 2 line or 4 line?
Putting the aesthetics aside (and personally I still can't decide either way), please can someone enlighten me as to whether there is any mechanical benefit to the COSC?

I've already taken a shine to one for sale in your classifieds however it 'only' comes with eleven links...is there a table that indicates size of wrist/number of links?

Finally, I need to sell a Yachtmaster generously given to me by my mother-in-law who I (now) won't have a word said against . I realise I can't sell on this forum yet, I am quite comfortable buying/selling on ebay, and I have emailed several commercial buyers for quotes; does anyone have any other suggestions for forums?