Question: I have some images that I want to use in my application ( 150 - 200 of them ).
What's the best place to store them? 

* assets folder
* drawable
* why there

Answer: 
**I don't think so there is bit difference in performance of using these two folders**, I think using drawable folder you can get easily images (All will be indexed in the R file, which makes it much faster (and much easier!) to load them.), and If you want to use it from asset then you have to use AssetManager then using AssetFileDescriptor you have to get those images. 

1. Assets can also be organized into a folder hierarchy, which is not supported by resources. It's a different way of managing data. Although resources cover most of the cases, assets have their occasional use.
2. In the res/drawable directory each file is given a pre-compiled ID which can be accessed easily through R.id.[res id]. This is useful to quickly and easily access images, sounds, icons...

and for more details go to this link:[Resources-vs-assets-in-android](http://www.gani.com.au/2010/06/resources-vs-assets-in-android/)
if you must put these images into your application pack, choose drawable that images will be compressed.
if you can download when required, store them in sd card is recommend.