a combination tool will never do the same job as a dedicated tool.
I have 4 grills...
A wood pit, I use this the most often, at least once a week.
A charcoal weber grill, second most used.
A pellet smoker that I also use as a grill, not often
A natural gas grill (paid $3,500 for the thing 2 years ago) that I have used 4 or maybe 5 times in 2 years (big mistake buying that thing)
so now you can see i am obviously biased, i would go for 2 grills if you must have charcoal and gas. I woul first try one of those charcoal grills that have propane starters, they make it pretty easy to grill in a hurry. That is if you can say grill and hurry in the same sentence.
Yeah, I also have a wood burning pizza oven so I like doing it the old fashioned way, WOOD!