Best value. Could be Spain.
As ridiculous as this seems, given they are Western European countries, I think northern Germany (NRW) and the Costa del Sol offer the best value overall at the moment. My opinion is based on travel (Frankfurt and Dusseldorf are major hubs and usually have cheap flights from most places; southern Spain always has endless offers available) ; ease of travel when you get there; language and communication; safety; cost of hotels and restaurants; and cost and variety of girls. On the Costa you can often get a week's holiday with flights for 200 euro from most northern countries so, even if you don't live in the UK, for example, it may be cheaper to fly there and book a holiday in Spain. All done on the internet easily. Only the Costa del Sol though. Other costas are more expensive (CIMwise!)
Read the partytreff treads in the German section as you will see that you can get 12 hours of fucking a great number of women for about 100 euro with food included. A good clean hotel will cost around 30 euro. I have been to partytreffs lots of times and had some amazing experiences,
On the Costa del Sol you can see from my many reports and photos how good the value is. It is a holiday place so hotels are there by the thousand at all price levels but a good quality room can be had for 35 euro. It is sunny here too.
Last year I was in Thailand. In Pattaya, the island, Bangkok and over near Burma. I posted reports here. I thought the girls did not offer good value. ST at 1000 baht plus 300 BF is about 30 euro. Plus all the girls look the same!
Russian and Ukrainian girls are the prettiest and sexiest (I am an expert on this, believe me) but their attitude is highly variable and communication can be difficult. I love Ukrainians the best in the world but they can be an enormous pain up the arse. All prices, for everything, have the foreigner factor added too so I don't think overall value is good. Plus the visa and travel costs are very high.
South America is exciting but a little dangerous if you don't understand it. Better for experienced travellers I think. And I speak Spanish. Paraguay has the prettiest girls for me.
Good luck!