I think its a matter of personal choice and also it depends on what you're used to. Apart from that it shouldn't make any difference to detail if you adjust the size of your brushes accordingly, you should be able to get all the details in. You might have to be a bit creative with how you use your existing larger tools. After 5 years of using 18x24 stretched canvas, due to cost and storage issues I recently opted to try 12x16 canvas panels. They were a little bit awkward at first as I had to introduce some smaller brushes, no need for a two inch for sure, and your brushes have to be sharp, no good trying to get away with using an old liner thats past its best for detail work, but I really like them now I'm getting used to them. I think the main issue now for me is how the finished painting looks on the wall, I prefer the look of the 18x24. I've done a couple of 3x3 and 5x7 just for fun and that's a whole different ball game. But I wouldn't go smaller than 12x16 now.