Perhaps not "more annoying" but "more obtrusive or noticeable". If someone want to fade into the background in a session while they are learning (which Mo seems to indicate is what is wanted here), a guitar tends to be a better bet than a mandolin, or especially a banjo, provided it's played tactfully, which isn't always the case. But too many guitars doesn't in my experience make for too good a session. More than two at a time is too many, I'd say.

Once again, there's the still quieter option of the ukelele in a banjo/mandolin tuning - which a fellow Mudcatter once suggested should be called a "mandolele".