Gameplay affecting (even if they're comparable or sidegrade items) just lead to people bailing because they don't want to deal with it. The objective is to lure those people into spending money, not turn them off because someone has some combat option or ability they don't (even if it isn't strictly an advantage).
As an example, in WoT I've spent maybe a hundred bucks on the game over a year, comparable to WoW. I spent money on 2 main things; 1 heavy tank and 1 medium tank (premium tanks, type 59 and Lowe), and a ton of garage slots so I could have all the tanks I liked in the game. I regret spending money on the heavy tank (the biggest purchase of the group) because it is easily duplicated by other tanks in the same bracket. I don't regret the type 59 because I know how to use it to it's full advantage and can take people out other tanks couldn't while abusing its high speed and manueverability. However, this gives me a gameplay advantage and isn't fun for the OTHER guy, making him less likely to play.
To boil that down - the two biggest things I spent money on are either A; not worthwhile to me or B; unfair to other players. The garage slots so far are my best investment in the game, I can play any tank I want to at any time, because I have room for it. IMO, MWO should focus on these secondary things for money, Mech garage spots, discounts on repairs, extra C-Bills earned, extra EXP earned, quicker Loyalty points, camo options (everyone, not matter how much they deny it, loves to pimp their ride).
Edited by monky, 10 May 2012 - 06:53 PM.