Both Blue Motors.
Which is better motor?
More reliable?

What are the issues with EFI's?
What are the issues with 502's?

Pros/Cons?
What you would run if you could run either?

Finally, has anyone ever heard of pulling 502/500 HP
heads "just because" Merlin heads are better? I know
Merlin has good products. But, doesn't Merc Racing put
together a pretty good package.

They are both 502's

So your question is what's the difference between the 500HP and the 500 EFI.

The only issue I know of on the 500HP is change the valve springs at 200 hours

Thought of another one , if the 500HP has the gil exhaust and the risers are low you have some risk of reversion.

Oh one other thing, I believe that the 500HP was blueprinted and balanced, the 500 EFI isn't.

Basically from what I have been told is that the 500EFI motor is a better motor. I have HP500 carb motors, I like them-- EFI's would be nicer, but much more money.

i thought you were supposed to change the valve springs on the 500efi at 200 hours also?