the one with the best previous work examples and lowest fees. Most retailers have their own in-house design teams and recycle the same ideas.

If you are talking display arrangements, the big corps have their own inhouse team to do that corporate branding or give the architect/interior designer the corporate standards to utilize and coordinate..  Smaller retailers usually do the layout themselves and coordinate with the architect on things like lighting.  Some others use the display furnishing supplier's inhouse designers... while others still use either a architect or interior designer to do it all.  Basically, roll a dice.

Hell, a architect I lease space to designs nothing but displays & kiosk and makes a good living on it.

its anyone who has the confidence and sound convincing.

We used to do a lot of retail.  We stopped, because the clients had unreasonable expectations, the schedules were crazy short, and the fees were small.

since retail is 90% of what i do i guess i can add my two cents:

what usually happens is that a company will hire a big, well known firm to do their prototype store.  the "in house" bit is usually a few project managers that send the work out to a few different architecture firms (like mine) to implement the prototype in various locations.  they ultimately make all the final decisions and try to preserve the "prototype concept", but the architect makes layouts, does site surveys, designs with a sort of "kit of parts" (mostly predesigned fixtures), and sees the project through construction.  pretty cookie cutter, but great for a firm that's looking for a steady flow of work (eg. 4 stores a year)  that they can streamline down to a formulaic process.  makes cash flow predictable, although its usually a very low fee and easy to lose money on a project.

the fun part is when you get the smaller startup companies that don't have a store yet (or a big budget), who want a small firm to do their design.  the design process is all about creating their brand, which usually doesn't exist yet.  while the small companies i've worked with tend to go with the cheaper stuff (lots of formica), they can be swayed by a design that really works well.

if you want to do retail, these should appeal to you in some way:

- millwork (tables, racks, display systems)... very detail oriented. i'd say most of the concept design stage is actually industrial design.

-interior design:  because aside from the millwork, that's all it is.  a storefront with some kind of box beam to hold it up is usually the most structural thing you'll ever work on.

-lighting:  hugely important to any retail experience.  the store is basically like a stage.  bad lighting will ruin a design, as well as sales.

-prototyping:  taking a design, doing it once, finding out all the problems with it (what works, what doesn't), editing, and building another one.  this is usually less of a pretty design thing and more of a functional, store operations or customer experience thing.  companies will also be figuring out what works and what doesn't work with their business in general, and a lot of the times their original concept of what the brand should be will change.

-retail operations/customer experience:  if you've worked in retail, you know all the rules.  there are things about merchandising that are pretty standard, and they usually don't change from retailer to retailer.

ultimately, once everything is designed and they keep making the same store over and over, its a drafting and project management thing from there on out, with a few design challenges here and there when you get a weird shaped store or ridiculous landlord requirements.  efficiency and getting it out the door ASAP is the priority.

hope that helps!