Define the word "best". It depends on what your requirement are e.g. superfast CPU for calculating PI to a zillion spaces, a great GPU for zapping all the Wall St brokers etc. My company considers "best" as being the cheapest device they can get away with. Others want a pc that will outlast an abacus.My experience is that what the user wants or needs is often diametrically opposed to what the company is prepared to let them have. This seems to be worse, the bigger the company. The bigger the company, the more the IT departments try to standardise on devices (always in the name of security).If you are in a company that gives you the device you want,,then you are lucky!
For a typical small business office setting and usage, full size tower for expandability, otherwise anything goes.