Dryers haven’t changed all that much over the years; they still perform a relatively simple function. The primary differences in the new models are the energy source (gas vs. electric) and a handful of features that are worthy of consideration: steam technology, moisture sensors, and vent block sensors.
Truth be told, most dryer purchases are driven by the washing machine selection. While washers and dryers don’t have to be purchased as a pair, that’s what most people do. Manufacturers have gotten wise and are designing matching washer/dryer combos to encourage consumers to purchase in pairs (and keep in mind that dryers are stackable only with the matching washer).
Trying to keep the cost down? Consider selecting a white machine (there is up to a $100 premium for colors) and foregoing the steam option (there is debate whether steam technology actually translates into fewer wrinkles as manufacturers claim). Also, electric dryers are cheaper and depending on your electricity source (solar vs grid), can be a more environmentally-conscious choice.
NB: While the models shown are electric, they are all available in gas option.