The main consideration in buying a vacuum is the flooring. Seems like an obvious point, but the vac should change based on hardwood, shag, oriental and berber carpeting.
We sell just Miele at Yale. It has variable speeds, a sealed system and different tools. The main differences between them is the flexibility of the wand and the head size and type. The better vacuums will have an electronic head, which is better on the oriental and deeper types of carpets....