It is my opinion that when the RS gold update to the cb begins, summoning will not be as effective as herblore, however after the revamp of summoning it should become a lot better.
Disregarding everything above I'd suggest using the xp earned on summoning because summoning is more benefit from the bonus xp because you can save money as well as time from collecting charms. Do you remember how summoning had the 1.1x multiplier for bonus xp weekends unlike other skills to avoid to be unbalanced? However, this time it's identical to any other skill, so I would take advantage of it if I had to summon extra xp.
I believe it's time I master this buy Runescape gold skill. At the moment I'm 63 years old in this skill. However, the only experience I've got with this ability (I mean actually doing it, not actually the training to reach a higher level), is from about five times when I was solo.