Dryer shopping often starts with drum size, cycle names, and sensors. Those matter, but the vent route decides whether the machine you pick will run well in the space you have. Work the route first, then compare the machines that fit it.
Measure the route, not just the wall
Trace the exhaust from the back of the dryer to the outside cap. Note the length of the duct, every bend, and any change between pipe types. Each bend adds resistance, and a long, bent route can slow drying. Write the total run on your list.
Compare pipe and hood types
Look at the duct material. Smooth rigid metal is the usual choice for a run like this, and thin flexible foil or plastic is harder to keep clear of lint. Check the exterior hood or cap as well. It should open freely and have a screen or louver that does not trap lint. Ask the installer to name the type they plan to use.
Check the machine's own requirements
Each dryer's installation sheet states the vent requirements it was built for, including the maximum run and the fittings it accepts. Read that page for every model on your shortlist. Two machines with the same drum size can have very different venting needs. A model that needs a shorter run than your house can provide is not a fit, however good its features.
Compare the hookup too
Gas and electric dryers need different supply connections, and not every room has both. Note the outlet or gas line already in place, and the clearance needed behind the machine for the vent hose or pipe. A tight closet may leave no room for the bends the route requires.
A short list before you shop
Write down the route length, the number of bends, the pipe material, the exterior cap type, and the supply you already have. Bring that list to the store or the bid. Compare dryers only among the ones whose venting rules your route meets.
For a general view of how long a dryer is expected to serve and when to plan for a replacement, see Clothes Dryer: typical service life and when to plan.