when you buy online - at least in my part of the world, you are engaging a third party. So, even if you trust the online dealer, and have heard great reports - and no matter how good their intentions, and no matter how dedicated they are to providing you with the best livestock possible, all it takes is a new boy with the courier to through your box about a bit, saying "ah its only a fish, it will get over it", and then your fish has had its lot.
My second gripe withbuying fish online is that you don't see what you are getting until you open the box. With some fish, you wouldn't care, as long as it is healthy - after all, a chromis is a chromis, a yellow tang is a yellow tang, semilarvatis b'fly is a ....... etc etc, but with angels in particular, one specimen might be very different to another. They might be both very healthy etc, but some fish vary ALOT ..... like queen angels for example, or coral beauties .... even flames. Sometimes my dealer gets flame angels that are red .... and I mean RED ..... other times, they are just a dull (by comparison) orange. With mail order companies, some body has to get the less spectacular specimens, or else they'd be left with thousands of plain ones........ so personally, I'd buy one locally - or I'd pay extra for "hand picked" specimens. After all, with angels, if you look after them you'll have them for 10yrs plus - at least I assume you aim to keep them as long as possible - so in my view, paying twice as much for a good one is small money compared to how much you'll spend looking after this fish for 10 years !!!
Another point to note is that even if you ask for a "nice one" - well your version of "nice" and theirs might be totally different. I asked my dealer to get me a "nice" queen - he went to the wholesaler and hand picked one for me - he arrived back with a solid yellow, rater elongated fish - he thought it was a beauty .... I thought it was plain. He ordered another for me ..... just any old one, and it came in with loads of blue etc on it, he thought it was a mutt - I loved it.
The last thing to bare in mind, if you are going to order a juv. emporer angel, or any angel in juv. colours, it could turn out any way at all ....... you just don't know.
HTH
Matt