Is Tamiya M03 better than M05? In which way?
 

Is Tamiya M03 better than M05? In which way?

No, the M03 is not better.

Weight distribution over the front tires. As long as track grip is not too high to cause traction roll.
Easier to change wheelbase.
Simplicity in design.
Lighter.

If you're running box-stock rules, the M03 is better as the rubber insert in the plastic shocks acts like a damper. The M05 has a much more crude sliding mechanism.

If you're allowed to upgrade to oil filled shocks, it's personal preference between the two cars. One of my fellow racers is much faster with his M03 vs an M05, but most of the others are the other way around.

The M03 is lighter overall by a fair amount, a lot more nimble but harder to drive. The M05 was a lot more consistent. I was always faster with the M03 over the M05.

I always enjoyed racing the M03. With the right conditions, it can be a very aggressive car. I need to put one back together. lol
The 5 has been a solid car, easy to drive.

It will all depend on setup guys...The m03 is still my favorite of all the M cars....

My personal feeling is that the M03 and M05 are both competitive against each other and w/ the same driver and comparable setup either (M03/M05) could outperform the other.
If you asked about the M03 or M05 vs M07 I'd have to say no comparison M07 hands down as it offers more tuning options (diff' and gearing).

Before the M07 came out we still had a few M03's competing against the M05's and there was no clear advantage on chassis alone.