which one is better ?

I've used Mallory magnetic breakerless for years with no problems yet. Cheap and reliable.

Why not use an MSD????????

If you use a Merc system, use a Thunderbolt IV and get a V-6 module for your blower motors.

I don't even know if a GM HEI will fit behind your blower due to the diameter of the cap. Also it will probably be more difficult to program the advance curve.

i didnt ask this for my blower engine;
i am asking this generally

I chose not to use them because of how many boxes I've seen cooked. Cook a box, no spare, YOUR STRANDED! I ripped the tundervolts out of my Sonic when I found out I could get the Mallorys for what it cost for the V6 moduals.