By nightlife, I'm guessing you mean nightclubs and such. If so, lower Sukhumvit may be where you want to be. A lot of the action is up Suk Soi 11 and the surrounding 5 block perimeter... also with plentiful street food options and umpteen restaurants.
Perhaps you don't realize how close things are. But the distance from the Intercon, to the Conrad, to the JW is not that far, a few blocks at the most.
The rooms at the Conrad are nicer. Whereas, the lounge at the JW is the best, by far. It depends if you're planning to spend much time in either.
Evenings, traffic gets nasty up and down Sukhumvit. Cabs reject many but the short trips. Soi 11 becomes a parking lot for hours. On other nights, traffic is not bad.... unpredictable.
Being within walking distance makes a big difference.
I say, JW or Conrad. But there are 100 other hotels in the area that would be just as good.