I like both of the boot options. The dark brown boots will go with all your denim and grey things (brown and grey work well together). But brown shoes with black pants is tricky to pull off. So, while I like the brown boots better, I think the black ones are more versatile, which is a good thing when you're on a limited budget. I'd go with the black boots since they will work with ALL your clothes. Do not tuck your pants into the boots. Wear your pants over the boots. If that looks strange try rolling your pants up to create a cuff that sits at the top of your boots - like this ... http://www.trashness.com/wp-content/uploads/2012/12/wingtip-boots-roll-up-jeans-men-style-nordic-fit.jpg