They do have a difference in usage. Indoor work most likely demands less usage, but an outdoor one is pretty high. So, you may need less than 20 pockets to complete indoor work while you may need more than for outdoor work. Although it still depends on the usage that you have to do. Most maintenance tool bags contain more than enough pockets to do so. So, first, consider your preference. You can get from 20 to more than 50 storage pockets in a tool bag. If you can afford then having a bigger one than the basic need would be even better for extra caution.