Normally I'd like to help but this is one of those occasions where only you can come up with the right answer. From my perspective though the Proxxon appears to have a better bed but might be seen as coming up short otherwise. It is a very tough call. The Sherline has standard tapers and apparently more adaptability.
From a non technical standpoint I'd have to go with the Sherline due to the excellent support they are known to give and the good relationship with the hobby world. Sherline is the product of a small business that appears to care about its customers. For me Proxxon is a more remote supplier of small machines.
All of that above however does not eliminate the other machines you can choose from, such as the taigtools.com. In the end the machine has to fit your goals, a small lathe can be a problem if you suddenly have a desire to do a larger model.
