It's good to hear that you want to play the long-term hold game as that is how you'll ultimately build equity.  

There's a high chance that you are feeling FOMO from the returns in public markets, sell your houses for a loss, pile into stocks, and then see mediocre performance while real estate heads back higher again.I see this, and similar actions, play out over and over.Personally, I'd stick with the real estate rather than selling it.

Most gulf front investments are mostly appreciation plays unless you do a serious renovation.

Playing the long game, it's not for those chasing rainbows, definently for the LT planned methodical focus. 

The STR, if purely an appreciation play,  is speculation to me. 

If you're aiming for growth and can secure a low-interest mortgage, financing might be the better play.

I have a contrary play. 

This campus hosts a large Magnolia home goods store, high end furniture store, cupcake bakery, coffee shop, gardening shop, live music concert venue, large grass area with toys and balls for kids to play with, an open plaza with eight food trucks, a small baseball field (that Babe Ruth once played on and families can now play on for fun), a restored historic chapel (the oldest chapel in Central Texas), and six boutique shops with men, women, and children's products.

Quick cash on a flip is going to 1. give you more cash to play with vs HELOC interest rates 2. give you an opportunity to 1031 exchange into your next investment. 

Location plays a big factor into this question.