I'd say spend your money on build quality rather than specifications. I have a lenovo thinkpad and am pleased. the think series seems to be better quality than the idea series. I have the x220 for travel and can run 100+ component assemblies pretty okay. I would really rather have the w520 or the w530 coming out in the summer. for integrated intel hd graphics it does pretty good though.
I have been very pleased with apple products in the past too. hp and dell have workstation lines that many people are fans of but i haven't used them.
saying you do mechatronics doesn't really help though. I think it comes down to how complicated you intend to get. if you're designing aircraft you need the best. if you're putting together small assemblies virtually anything new is going to work. I'd say go with intel hd at the low end, quadro series gfx at the high end. for school you'd probably be happy with the intel hd graphics.