How to discern quality of a breakout board? other than proper soldering on back of board
How would i know which is of higher quality?


Quality, in this context, usually means life expectancy and life expectancy is dependant on many factors such as: -


How the boards have been handled previously
How the boards were made/soldered
Component deratings when in use
How or if the boards were tested during production
Recommendations about how to properly use the boards


Most of the above comes down to buying from a reputable dealer who, in turn, only handes products that meet certain design and manufacturing standards.

Alibaba or ebay does not reckon on my top 100 list. Why do you think designers of aircraft and missiles etc take such a lot of time working out failure modes and component deratings whilst ensuring that the components bought have a well-defined history through manufacturing and shipping.