The ones that have highest visibility (talk, advertisement, exchanges, coinmarketcap.org, etc) by the time they look for better-then-Bitcoin alternatives times the prospect of higher valuation and/or other features that may appeal to the potential investors (like anonymity, adoption, logo, etc.).
If their aim is to find a better speculation vehicle, the competition is broader then only among the anonymity minded coins.

In any case, user friendly GUI and use experience will definately help to attract fresh blood.