X4 is more future proof to be sure. Also, it performs much better over all when multitasking and non gaming applications are considered (Like winrar to unzip your newly bootlegged games). I just don't like how slow it is in some cases. If you have the money spend a bit more for a faster quad.
Also, I don't understand overclocking. I know too many people personally who fried their CPU & MB, because X% OC wasn't enough and they wanted Y%. The small performance increase from OCing is not justified in my opinion, considering the risk. Also keep in mind that the benefit is not one to one, for example if u OC by 20% the performance improvement will be less then 20% with an average improvement of maybe 15%. This gets worse the higher one OCs. So a 50% OC will get maybe 25% more performance on average. Also, to get any real OCing u usually need to invest money in cooling. Most stock processors can only achieve maybe 10-15% more performance from OC without investing in cooling. Notice i said 10-15% performance not clock speed increase, the two are not the same. Since we are talking about 100$ CPUs here, it would be better to invest the money in a better CPU.