Macbook pro mid 2009 - best operating system?

I have a 2009 Macbook Pro 15" with Snow Leopard as its operating system and I'd like to upgrade. But I've been unable to put El Capitan on the machine after trying a bootable flash drive as well as downloading from Apple and installing. Yosemite is the only other option from Apple's website. Is there a reason anyone knows why I shouldn't try Yosemite? Is there anything I need to know like the date change issue required to get El Capitan to work?