Your new boot should feel snug around the ball and instep without having to strangle your foot by cramping down on the laces. If your toes are tapping against the front of the boot, you should go a half-size larger. Check the fit even more by lacing the boot snugly, then walking down an incline to see how much your foot will slip inside the boot. Once fitted, stroll around the shop for awhile. Don't stop at just trying on one manufacturer's boots.
Every manufacturer builds boots around different lasts.
One manufacturer's lasts may just match your feet better than another's. Besides, each company has a different philosophy about where the padding should be, and how much of it there ought to be in any given part of the boot. Now, at some point in this game, hopefully before you completely exasperate the salesperson. Grimace if you must, but part with the cash that will keep your feet comfy. Regardless of the type of boot you buy, they will need to be broken in.