Burning in a Transistor amp, does it change anything?

This seems to be a 'marmite' subject, many say that it doesn't change a thing and others say that you should burn it in for at least 10-100 hours(depending on who you talk too)!

I understand that warm-up and burn in times on tube amplifiers matter however I've just restored a NAD 3020B, replaced the main transformers and most of the power supply stage (excluding the transformer and the new filter caps are 4800ufx4 from 2200ufx4) and I compared it to a NAD 3020B I already have with 0 modifications from new.

Both have the idle voltages and output voltages set right, the transistors in the restored NAD were matched by Hfe, both amps have Motorola transistors and the input is exactly the same (going straight to the power-amp, avoiding the pre-amp). Also the rest of the transistors are the same on the circuit, I know how NAD liked to use what was in the parts bin rather than sticking too the drawings.

Despite all of this the older NAD sounds better, there's more low end and it sounds more controlled, and It's not just me that thinks this. I'm interested to see if anyone has experience of burning in transistor amps, and if they sound any differently?