If you have a couple of nickels to rub together, then srping for a nicer, tailored suit. Not only will it look nicer on you; but it will also fit better and therefore not cause you to fidget & squirm cause your pants are riding up your ass or your crotch is hanging half-way to your knees.
Ideally, your suit should not be what the interviewer focuses upon. The focus is you, your application, qualifications and your presentation --> YOU! Personally, I picked up two suits, Men's Wearhouse frequently has 2 for 1 sales as does many other men's clothiers, and both were tailored to fit me nicely. Then, for a personalized touch...HATE looking like a funeral home director or any one of those plug 'N' play "power" business suits (dark suit, white shirt & stick-in-the-ass conservative tie)...I chose bold shirt colors w/ coordinating ties that complemented my suits. That made it easier to pack for multi-interview trips.