The biggest difference is obviously less tourists and less bg's, but saying this I always preffered low season to high as there are still more than enough girls etc and you get more space at the bars or whatever you want to do.
Chances in June is that it will be hotter during the day but odd rain, usually in June not too much and only for short periods. Saying that this year the weather does seem different to most others I have experienced before, so who knows. I do also like the rainy season (July - Nov) as a short sharp burst of rain freshens the day and takes a little heat away for a bit.