Personally, I think the “cache” thing goes both ways.
Yes, using your own name is obvious if it is already established or you jump onto the market with a lot of momentum, for example if a designer opens his own shop after heading another design firm successfully for years.
I feel that going with a branded name should generally be reserved for firms where several people are involved.
Personally, if a designer wants to set up his own freelance shop, I’d recommend going with your own name.
Of course, a catchy name helps. If it is say a Joe Schmo John Smith kinda thing, why not go back to a cool nickname or invent one that believably could be interpreted as an actual name. Actors do this all the time.
Branded names from young designers looking for freelance work that try to be whimsical or clever just feel contrived and a bit silly to me, in the worst cases just arrogant and ridiculous.
No client will refer to the freelancer by his brand name anyway if it is only that one guy. I feel that if there are several people involved, a name which everyone can stand behind, makes a lot of sense.