I prefer suit. No matter how hot it is, if you want to get the job, sacrifice a little and wear a suit. In addition, everybody should have at least one set of suit made of light weight wool. If you only want to buy one set of suit, make sure you go with light weight wool as it is very versatile.

I don't want to see people wearing just shirt+pants personally (financial industry), but if you have no choice, make sure the shirt is tucked in and wear a nice and simple belt (also match belt's color and shoes' color).