I bet if you and your friend walked into a guitar store to by new acoustic guitars you two would buy guitarts made from different woods. You seem to like a deeper, richer tone. Your friend likes brighter tones.
A pick gives brighter crisper tones wheather your picking strings or strumming chords. It also limits the amount of tones you can get from your guitar.
Using your thunb and fingers will give more mellow tones, but you can make your guitar have so many different tones you can't get from a pick.
Depending on what part of your finger you use to hit the string you can make the srting(s) sound different. Use the front of your finger, side of your finger, use part of your nail as you hit the string. You have more fingers to use to pick with grab strings with and pull off of while your thumb strums other strings.
Don't throw away your pick, but never feel you have to have one to play acoustic or limit the tones you can create by always using one.