If I recall correctly from my research ... the YTZ series are gel based, are smaller and have more capacity than the YTX series which are liquid based. So a YTZ14 will fit, whereas the YTX14 would not. You can get the YTX factory filled, or dealer filled.
I do not do any winter riding (no kidding!) so I went with a straight YTX12 replacement from 'total Battery' that cost me $64. The YTZ were about 50% more expensive. I needed the battery immediately and the YTZ were special order.
My dealer wanted $137 for he Yuasa YTX, and over $200 for the YTZ14.