What would be the benefit of being in a shared rack? Wouldn't the service provider still know which physical system is yours if you only rented a 1/2/3U space? (Or is there an advantage at a network layer?)
The shared part is only for pricing, since renting a full rack for a single server is a bit overkill :)
Going for a rack has the advantage that you own the hardware and can install the anti-tamper measures so that the server can't be turned against you. Anonymity wise, renting a server makes things a lot easier.
What would be the benefit of being in a shared rack? Wouldn't the service provider still know which physical system is yours if you only rented a 1/2/3U space? (Or is there an advantage at a network layer?)