1. Ask each to "demo" a comparable unit that you are want to buy. Gives you a chance to see the unit in person and how the truck function are controlled & see which one best fits your needs & likes/dislikes - not all lift trucks are alike
2. Evaluate each dealership as to there support capabilities to keep you up and running - parts, service (number of service vans on the road, # of factory trained techs, rental (do they have a similar unit (s) in their rental fleet to support you in case your machine is down for a period of time), service response.
times , etc.
3. Do a spec sheet comparison - turning radius, width, length, height to top of overhead guard & top of mast when lowered (consideration when going under overhead obstructions, like door ways, pipes, etcetc and get the net rated lifting capacity at full lifting height as the unit will be equipped. These are all basic rated 4000 lb units built on a small frame (most lift truck companies have two 4k units one on a short frame & one a a larger frame) but if equipped with 3 stage mast (etc the net capacity more than likely will be less & you might. The large frame units is longer & wider, bigger drive & steering tires but has a "more solid feel" & rides better & usually better capacity retention but cost more), the short wheelbase unit is more maneuverable but has smaller tires (rides not as a smooth), tire replacement especially the steering tires will be more frequent and the net rated lift capacity would be expected to be less.

4. If all comes out equal in your view - then base your decision on where each sales rep takes you to lunch/dinner or both.