Tourist L or Transit G Visa

Hi, I'm traveling to Korea in October. My flight is from Seattle to Shenzhen with a 2 hour layover, and then from Shenzhen to Xiamen with an 18 hour layover, then from Xiamen to Incheon, Korea. On my flight back I fly from Incheon to Xiamen and have an 11 hour layover, then I fly from Xiamen to Shenzhen and have another 2 hour layover before I get back to Seattle.

Because I have a layover in Shenzhen, which is not a city where you can be in without a visa, I need to get entry permit. It seems like I need a Transit G but I was wondering if I could get the 10 year Tourist L since it is the same cost. Because if I will be traveling through China in the future I might as well get the 10 year entry permit if I can.. I just don't know if it's valid for this situation and if they will accept the Tourist L if I am only staying in China for less than 24 hours at a time?

Thanks