As a Singaporean, I love my country. But I have to say this, our tourism isn't that all fantastic. We have a rather limited selection of theme parks which can be easily found anywhere else in the world. We depend heavily on tourism for revenue, yes. But I think they have been doing a rather poor job at that. Tourists never really get to see the REAL Singapore unless they were backpackers or here visiting with Singaporean relatives. I don't see the point in tourism if you just visit a few theme parks and learn nothing of our country's rich culture and history... Oh, and be prepared to burn a hole in your wallet. Everything near tourist attractions have inflated prices. Such that you can buy bottled water for S$3 in Marina Bay, but if you go to a neighborhood or supermarket, it's like 50 cents.
To answer your question, yes we have pretty good infrastructure. It's easy to navigate and there's plenty of public transport. Most people here speak fluent English so you don't have to worry about communication barriers. As for accommodation, the closer you are to the CBD (Central Business District) or 'Town' as the locals call it, the more expensive the hotels get. Our roads are super clean. You can drink straight from the tap. And we are a very safe country. You don't have to worry about getting mugged.
Korea on the other hand, has done an excellent job. There's a HUGE variety of things to see and experience. If you pick a good tour package, they will show you Korea's natural heritage sites. (Jeju Island is a MUST go!). Some offer trips to the villages and even offer kimchi (a local delicacy) making courses. They have loads of interesting local theme parks apart from the mainstream. If you are an avid fan of Korean dramas (I am), some tours offer to bring you to the very scenic locations where they filmed the most famous dramas. Clothes, trinkets, etc are dirt cheap there. They have much more to offer rest assured. Every single friend of mine who went to Korea never came back disappointed.
As for infrastructure, theirs is as good as Singapore's. Some regions more high-tech even. However, not all the locals speak English and most of the signs are in Korean. So you'll have a pretty hard time if you're backpacking or not in a tour group. Accommodation is relatively cheap according to my peers.
It's really up to you. But if you want a meaningful experience with both city landscapes and beautiful nature escapades, pick Korea. If you want a safe, money splurging trip; pick Singapore.
I'm sorry to other Singaporeans who are reading this. But I am only speaking the truth. Our tourism standards are good. It's just that they have robbed the meaning of 'tourism' and turned it into a money-making, overproduced franchise. I am in no way insulting our beautiful country.