Out here in the colonies we take what we can get! It is rare that we get a chance to try both owner and independent bottlings of the same distillery here. We're glad to get whatever independent bottlings are sent from distilleries which don't feel it is worth the time and money to export to other countries (different bottling regulations, etc.).
At least with a single cask IB if you like a particular cask it is possible to get another bottle of it. With OBs sometimes I absolutely love one of their standards and years later I buy another bottle and only the label is the same, the taste is now completely different. Some say this is part of the joy of single malts, the inconsistencies make it fun, but if they're going to vatt the stuff they should get it right! Differences are alright but going from great whisky to bad is not a good inconsistency. When you have a cask number you know (poor bottles and corks aside) what you will get.
Another point for independent bottlers is some allow you to get whisky which is not coloured or chill filtered which allows you to get a different taste. Some are better chill filtered, others are better unfiltered. Now that Ardbeg, Bruichladdich and others are going unfiltered for their OBs this isn't as important but others will continue to send us 40% ABV, filtered medium grade scotch.
There is snobbery all over the whisky buying population. Some whisky societies advertise that they only bring in whiskies older than 15 years -- why? Nonesense I say to those who claim you can't have a good whisky aged less than so many years. Other people will tell you that old whisky is just whisky that was still awful at 8-12 years and they're just glad that it got better rather than worse, and then fell over themselves when people wanted to pay huge money for this old stuff! Some insist that the best stuff goes to blenders while the unacceptable casks sit around for years of additional aging to sell to whisky snobs who don't mind paying top dollar for a number on a label. Who knows what is true?
My rule is I drink whisky because I like it. If I can only get an OB or an IB then that's what I drink. If I happen to prefer an IB over an OB in the rare case where I can get both, I'll drink the one I prefer. If I happen to favor an older version, I'll drink it; if I prefer younger, all the better. If I don't like one, I won't buy it again and after a couple of strikes against a distillery or bottler I may not buy anything from them in future.