I find a sirloin steak does benefit from a marinade as it tends to be a leaner cut. I don't buy them anymore because of that.
I prefer to taste more beef than marinade.
Everyone will have their methods and desired cuts of beef.
Now, my preferred method is to cook striploins with some nice marbling. I do the following:
No seasoning before the beef steak hits the grill.
After the first flip, I sprinkle some steak seasoning on the first seared side.
Then after the second flip, I sprinkle some more seasoning on the second seared side.
One or two more flips, and it comes off for a 5-10 minute rest. It's simple, and it turns out delicious!