B1/B2 or K1 Visa

[rwagga]

So I have a girlfriend in Philippines and want her to visit me in the US to meet my parents. However it seems like there is a high failure rate with the B1/B2 visa for Philippines citizen. So what is the down side of just doing the K1 visa and letting it expire? As she would return after 2-3 weeks.
https://vlc.onl/
If we do decide to get married at a later time can I do another K1 visa with the same person?