Basically , LM2577 and XL6009 are same ,with differences of pins arrangement , currents (XL has 4A , LM has 3A ) and internal oscillator (400Khz vs. 52Khz ).
Also , XL6009 has an enable pin , good for start -stop by external signal ... For me , it looks like XL is a better version !
The second module (LM2577 & LM2596 ) is good for charging , I'm using one for charging Lipo ,recovered from different appliances. It is ok . And you're right , the price is...
Thanks for share.., and if a 250W/10A will be on your work bench soon , I have some tips for making this particular converter a real 250W one !!! (at this moment I modified , tested and mount 27 pieces in different led light projectors , for inside and outside purposes , houses ,motels ,museums ...)