If you're never going to push the BMS with high inverter loads AND the Eco worthy fits nicely AND saving a few quid AND the ease of hooking everything up appeals then the Eco worthy's plusses could outweigh the slight increase in theoretical reliability and convenience should a fault occur.
When it comes to predicting reliability of electronic components it's almost a coin toss, stress (heat) will shorten life of any component but some components are unpredictably (for the likes of you and I) less resilient than others so nothing is a given. I myself typically end up going the cheap route mainly because when stuff fails I can repair it but I'm fortunate in that sense and I don't mind using cheap chargers, inverters, etc rather than forking out for Victron etc al.
I guess if the Eco doesn't fit and 3 singles do then that'll be the clincher anyways