If you can get your peep to come around perfect without mistakes than going without the rubber tubing is always best....BUT...for peace of mind, go with the tube....the tube is noisier however.....

I've never shot with the string loop but will on my new setup....I was under the impression that the string loop aligns the peep as well....if set up correctly....

ps. you can also train your peep to align properly on every draw once the string is broken in.