In my experience actual root -- either medium grind, micronized, or instant-- gives a more potent experience than extract. However you need to consume about a tablespoon of micro or instant for an effective shell. That would involve filling and swallowing a lot of capsules. Why don't you just get micro or instant and mix it in water and drink as normal? Perhaps you don't care for the taste? lol..
Between micro and instant, I find they are about equally potent. Micro is much less expensive, but (only talking about my own experience here) harder on the stomach.
If you really want to take a capsule, you will need to use extract, but it will not be as powerful an experience. There seems to be some stuff in the root that is not extracted in the extract that makes it more potent..