Just because your horse isn't slobbering like a rabid dog doesn't mean that they don't like the bit they have in their mouths....As a matter of fact.... I don't really remember any of my western horses slobbering like a lot of english horses do. That being said... I just bought Dumas a new bit that is the exact same as his old one it just has copper rollers on it now....The old one was getting rusty and really crappy looking... I guess I'm saying here that I did upgrade when I replaced the bit... but only because he could use a new one.. not because I wanted a wetter mouth or harsher bit.
I would not go to a harsher bit... maybe one with inlays might be better for slobbering but I would rather see you spend that money on a pretty new pad ( I have seen a TON of darling english pads...) or a set of new reins or somthing like that.....lol...but that's just my opinion.
I went to a John Lyons clinic one time and he gave me an Ahaaa. Moment..... Your horse was started on a snaffle....which is when they are the toughest and don't know anything....right...so why wouldn't your horse get better with age? Do we get dumber as we get older? No of course not....so....the bit is fine...its your butt that needs work.
<---totally said to make you smile... I'm not being harsh