I have a snake who only eats in the tub.
All three of my snakes eat in the feeding tub, and get excited and agitated when they realize where they are. My baby has actually snagged a jumbo mouse in the air before it even hit the ground a time or two (and it's not like the fatty is starving to death, either).
Shy snakes and problem feeders should be fed where they are most comfortable, but most "outgoing" snakes that I've encountered have eaten without any problems in a feeding bin. One memorable ball at work took a mouse, constricted it, and then began swallowing it all the while I was holding it (There's a story behind that).
Dave made an excellent point - feed where you and the snake are most comfortable. If you get a great feeding response when you feed in the cage, without any problems, then by all means, feed in the cage. That goes vice versa - if you get great results in a feeding tub, then use the tub.
Different people, different methods of feeding, what does it matter as long as the snake has its needs met?
~jenny
-----
1.2 normal ball pythons (Cindy, Darwin, and Periscope)
0.2 rescue chinese water dragons (Yoni and Linga)
1.0 rex rat (Scurvy)
1.0 gerbil (Yerbul)
1.1 mice (Cute Girl Mousy and FuzzBucket)
0.1 bunny (Spazz)
1.1 betta fishes (Vicious and Killer)
2.2 great danes (Shasta, Odysseus, Merlot, and Watson)
1.0 fat fuzzy mutt (Smokey)
1.1 cats (Thidwick and Turtle)
3.0 horses (Buddy, Sam, and Scout)
1.0 goat (Billy Jack)
1.25 chickens (Ugly the rooster and his harem)