I've only ever bought one Korean DVD, Sam Peckinpah's Cross of Iron. It's an extremely violent film and it wasn't cut at all. Neither, I believe, is the Korean DVD of Bring Me the Head of Alfredo Garcia.
I used koreandvds.com and it cost approx. $4 airmail to the USA. Super-quick service, too.
You can also buy Korean DVDs at yesasia.com (great site). Shipping is free for orders over $39. They sell higher quality DVDs than koreandvds.com. I have Korean edition of "Gloomy Sunday" and it is censored for nudity.
It's not a dumb question, but it cannot be answered with a simple yes or no. Individual titles vary, and you really have to do some research if you're looking for the best available quality worldwide. The Cross of Iron DVD that I mentioned is arguably the best version out there right now, but it may very well be superseded by next month's US re-release.
DVDCompare is a useful starting point. They list the basic specs for many worldwide releases, but, unfortunately, they don't go into great detail about the picture quality.
DVDBeaver compare screen-caps for different releases, but their scope is not as wide as DVDCompare's.
Other than that, all you can do is Google for reviews and read message boards such as this. Sorry if that sounds a bit obvious, but sometimes obvious is the way to go
Brett: I don't mean to sound obtuse, but it really does come down to individual titles. There are thousands of R3 DVDs - good, bad, and indifferent. Just like R1, it's a toss-up between quality, extras, and price.
All I know about your tastes (from your Japanese e-tailers post) is that you are interested in Last Action Hero.
This page at DVDCompare lists 92 examples of R3 DVDs that, in their opinion, are clear winners. Most are fairly recent releases, and in many cases the transfers are likely identical to their R1 equivalents. Where R3 often wins is by providing additional DTS audio tracks (if that's your thing).
It helped -- thanks. I can be obtuse sometinmes, as well.
All kidding aside, I just wanted to go into this with as much info as possible. I have an Oppo tricked out to all regions and I love some of the non-region 1 releases for their extras and packaging (Equilibrium region 3, Conan the Barbarian region 3, Last Action Hero region 4, etc). This is where I go to learn before I take the plunge.