I simply like the Island and have some friends there, so visit for a spell every year. There are some good dives, but it is far from similans standards. As you quite rightly state it is far from the best dive destinations, but I have generally enjoyed the diving I have done there, and have had some good times.
However from numerous dives I have done never seen anything like 25m viz, no whalesharks etc etc despite some of the promises made to me at times.
Offering another perspective on Koh Chang....
I drove my car there, and found the drive from Pattaya enjoyable. The ferry to Koh Chang was interesting as well. I found driving on Koh Chang thrilling at first, up-and-down and curvy like a roller-coaster.
However, after a few days, the thrill of the narrow dangerous up-and-down roads turned to a kind of "driving stress" where I began to really dislike driving there (takes too much concentration). Folks zip around the curves into your lane making driving quite dangerous and a "full attention span" affair, not relaxing. One day, I literally saw a group of tourists on their small motorcycles terrified at the top of one hill, afraid to go down, and this was on a bright, sunny day. Rain and storms changes that to a nightmare. Imagine combining all of this with alcohol. I heard some horror stories from locals (speaking in Thai to the locals about this). They say the busiest place on Koh Chang is the hospital treating people from roadway accidents. I can easily see why.
Adding insult to injury, my car was vandalized at the parking area near the fishing village entrance. Lucky for me, the damage was only "key into the paint" scratches, but none-the-less, it takes time to have this fixed, and of course, I will lose my "less than two claims, or was it two or less claims" insurance discount next year if I claim the damage!
So, when I combine all off the above with a "less than optimal" wide variety of places to eat (compared to Pattaya and elsewhere), and the fact that the diving was no better than Pattaya (especially the outer islands), and that Pattaya has much better wreck diving.....
.... I "hightailed it" back to Pattaya and was much happier there. I am glad I visited and did a few dives there, but I can't recommend it, based on my interests, and the fact I drove there. Perhaps being "wheeled around" in a bus is better? But then again, I saw a songtaew full of farangs rolling backwards going up one hill, while the farangs in the back were absolutely terrified. One young woman was in tears she was so frightened.
Back in Pattaya, I was out diving the other islands with one of the larger dive centers, and even though the visibility was not good, the fresh cooked Thai food on the boat was excellent, and the boat was very comfortable for diving. I also found the dive team very professional and well organized, and the customer service was good.
I know LK has had some bad experience in Pattaya, and I agree because I have had some bad experiences their myself. On the other hand, I have had some very good experiences in Pattaya as well. The good thing about Pattaya is that there is so much to do when not diving (and I don't mean bars with working girls). I am talking about sailing, yachting, and other water sports, plus some good golf (albeit too hot this time of year for golf) and lots of good places to eat (especially Jomtien beach area). Plus, Pattaya does have some very good instructors, based on my experience as a "just a wee bit more than a novice" diver.
Based on my trip to Koh Chang, I don't think I'll dive their again (anytime soon); but not so much because of the dive centers, fish and reefs, but because of the dangerous driving conditions on the island (especially during the rainy season and at night), and the lack of "other than diving" activities.
..... that's my "1 bar" contribution to the Koh Chang discussion
