Re: Which would you hire: architect or certified interior designer?
As with all trades, get references, especially ones where you can go and see their work. Having ideas is one thing, having functional ideas is quite another. A lot of architects/designers get trapped up in design over function, when it should be the other way around, function first with a flair of design to spice things up. Make sure that you give plenty of input to how you use the space and specifics of what you need/want, it is their job to incorporate those ideas into their own.
I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!