There would probably be a short delay in getting a replacement from
a jobber on most smaller titles as they tend not to carry obscure titles
in stock but order as needed. If you get defective copy, you will return to
them and they will return to the distributor for replacement.
My personal opinion is that jobbers are good if you want to order a small
number of titles from each of a lot of different companies. You can get one
stop shopping and a consistent discount. The more high end educational
distributors ( Women Make Movies , First Run Icarus etc) don't generally
sell their stuff to wholesalers so you would still have to go there directly
for the product. My biggest concern as a distributor is that institutions
understand that jobbers can NOT offer PPR or other additional rights so you
always need to got to the source if you need that. If you want to buy
either a lot of titles from one company or a lot of titles of one copy you
may get a better price dealing direct.
Frankly it depends on your needs and you can just see how it goes