Say, for example, that you are a pretty strong climber but a nervous descender. Do you buy a nice light XC bike so that you can climb even faster and accept that you will always be slow on the way down, or do you buy a big bouncy skill compensator to try and make the downs a bit more fun (given that you'll still be at least average going up).
Or, say that you struggle to keep up with your mates on the climbs, but kill them going down. Do you buy an XC bike to help you stay with the pack going up, or a big sled so that you can really thrash them going down.
In short, do you tend to buy bikes to enhance the stuff that you are already quite got at or to compensate for your weaknesses?