The 150-600 is close to 2kg, while the 55-300 is 530 gram - I guess that has a 'slight' impact on the walk around aspect.
The 55-300 isnt great, far from, but it all depends
you cannot get:
Great
Light
Cheap
For high focal, they are expensive and fairly heavy.
Cheap, light and less great is a good starting point, atleast you'll get some of the extra reach.