
Let me play devils advocate for a moment...
First off most camera stores, at least local ones, have 1-2 copies of ANY lens and they usually let customers play around with them, And then sell that lens as brand new in box anyways....And usually you're paying a good 10% markup on said lens..Sometimes they even put a return back out on the shelf as brand new too to be resold to another customer...Yes, Seriously, So guess what? You buy a "New" lens at a local store and its probubly been sitting there a year or two and has been played with by a few hundred people...
Its not just local retailers, theres some evidence that some online retailers, Not necessarily B&H or Adorama, but Amazon has resold returned products as "new" before, IE a guy here got a 70-200 f/4L in a 70-200 f/2.8L IS II box from Amazon, Other people have had similar times getting lenses with dust or that show they are not quite "Factory fresh".....In reality, most users wont even bat an eye about this unless the thing has very OBVIOUSLY been used heavily...
As for renting, you're paying how much out of your pocket to rent 2 lenses and etc etc etc... Not the most economical thing
Stores like B&H and Adorama have 30-day no restocking fee no hassle return policies for a reason, They want you to be satisfied even if it is YOUR mistake or if you ordered the wrong lens, The overhead and cost of dealing with returned merchandise is simply part of their operational expenses...Both are large companies and both can take a little hit...
Do you know why? Because when you go to buy another lens, you're going to remember that B&H and Adorama have a great return policy and dont give you 5 gallons of **** to return something, Meaning you're likely to do business with them again when you buy another lens...
If returns and that hurt the bottom line hard enough, then yes, they would charge a hefty restocking fee like most local stores do, The difference is B&H or Adorama are massive companies and can absorb the cost whereas your tiny local store cannot and has to charge a restocking fee because they'd go out of business otherwise
Dont feel bad about it, Order both and return the one you dislike/hate/etc, Its really not a big deal
-edit- and yes, I'm guilty of returning lenses for reasons besides "Defective" But you know what? If I did not have the option to return something, I'd never buy it in the first place
I completely agree with this. Stores know that sometimes you'll purchase a couple of lenses just to test one out for a couple days. Like mentioned, they offer 30 day guaranteed returns for a reason. There is NOTHING unethical about this at all.