When you first start out all guards are new. Nothing will work great, but some will work better than others. Over time, this is the guard you will spend most of your time using. This is partially because it will be the most rewarding, but also because it will be the guard you are best able to get to and maintain. The process becomes something of a self-fulfilling prophesy: you’re good at the guard you’re good at because you’re good at it!
This is how I developed my guard game until very recently. My closed guard and a sort of bastardized collar and sleeve open guard represented about 90% of my guard skill. But then I saw shin to shin and I knew I wanted more from my guard.