This question is very important for conference managers in Turkey. For example, our conference (October 2019, https://www.intraders.org/october/ ) presentation language is English. We are close to İstanbul and we have 3 nights İstanbul Program.
For me, the most important factor concerning the choice of conferences to attend is the topic. I only want to go to conferences that have a very narrow topic relevant to my research interests. That way I know I'll be able to interact with people who are interested in the same things I am.
Agreed with David. Relevant topic and easy to get to location (airports nearby, etc.). Time of year also important - not during term time if you want academics to attend.