White shores and the most stunning aqua blue waters you'll ever see, Thailand and other coast-side spots in Southeast Asia such as Penang, Malaysia, are popular holiday destinations. They bring together cultural heritage, mountain views, elephant camps, ancient temples and palaces, stunning beaches, water sports, resorts, restaurants and nightclubs -- all in one place. Popular Phuket destinations include Karon, Patong and Kata Beaches. Hotels, resorts, B&Bs, or half/full board accommodation are all available.
Pattaya and Phuket are the most developed beach resorts in Thailand, and both receive millions of tourists every year. Phuket has some very nice beaches, but every year it is getting more and more crowded and is very expensive compared to almost anywhere else in Thailand. Pattaya is much cheaper, but has a mediocre beach and dirty water. Most visitors here come for the bars, discos and prostitutes for which Pattaya is internationally famous/infamous. Phuket's Patong beach seems to be rapidly developing into a mini Pattaya. Due to the amount of tourists there, both have developed into very good areas for all kind of watersports.
Pattaya is only 133 kms from Bangkok so it is easy to get to. Pattaya is best known for its bars and night life but as you say beaches aren't of much interest to you so that doesn't matter. There are many things to do during the day like go to Nong Nooch, the Tiger Zoo, Big Buddha up on the Hill, Koh larn (island) a 45 minute ferry ride away...etc etc... There is one big benefit of Pattaya over Phuket, it is less expensive and the entertainment offered is of high quality, there is literally 1000's of venues to choose from. Pattaya is not or prudes though, if you are offended by looking at bar girls working in open air bars then perhaps it may not be for you. It shouldn't affect you if you and your partner are broad minded.
Phuket is about 900 kms south. Will take you all night to get there by bus or you can fly in an hour. Phuket is a beautiful place with everything on offer for the tourist, trouble is it is expensive. The beaches are better but that does not concern you anyway but it is very beautiful. I always hire a motorbike and Phuket is an ideal place for riding around on. Plenty of bars and venues there too but just more expensive hope that helps.