conventional, (Buddy Rich), and matched grip... BUT.. by FAR I use conventional most often. I started that way... and conventional I'm much quicker with my weak hand, my left. IMHO conventional is easier... but that's 'learned' or 'muscle memory' opinion.
My guess is that it's what you started with. I saw a Buddy interview where he gave his case for why conventional was better... (buddy was an arrogant SO
... but I didn't really buy it.
I will say this, but this is only one mans opinion.. 'technically' I am MUCH better using a conventional grip.. but getting around the kit is, for me, much easier using matched grip even though for me it restricts 'technique'.
In the end I don't think one is better than the other. Most of the drummers, not all, that I have admired most over the years used a conventional grip... but I think that was more circumstance than a deliberate decision... they learned that way. But those are the 'old days'...
I never counted but I'm pretty sure today most drummers use the matched grip... that's certainly true in rock bands. That kind of jibes with my theory about being easier to get around the kit... most riffs today in rock music require incredible speed but 'single strokes'... or very basic paradiddles.
If you watch Thomas Lang and Dave Weckle, (for example), they often switch DURING songs. That leads me to believe that yes, some riffs are easier with a specific grip.
In another thread I mentioned that I'm cleaning my garage right now.... like to say it's because it needed it, it was cluttered beyond imagination, but the truth is I want to set my drums up in there.