My limited knowledge
Shimano Gears from worst to best:
Budget 8speed
Tourney
Altus
Acera
Alivio - Decent quality
9 speed
Deore - Good budget groupset. Shifting is rough but reliable
LX - Excellent value for money - new rear mech is the old XT
Hone - LX, but black...for a while...then silver.
XT - Most common - performance close to XTR
Saint - Freeride specific - Tough
XTR - for rich people and racers. The best of the range. very crisp shifting.
Sram -
3.0 > cheapest
SX 4.0
SX 5
X7
X9 >XT
X.0 > XTR beater?
Sram Shifters
Attack - somewhere between LX and XT
Rocket - Alu body version of Attack - slightly better shifting