Best for what? Do you want to grill, smoke, roast, or bake? Use it also as a griddle? Roast on a spit? Or some combination?
Not every grill does everything. Some of the best for grilling don't work so well for smoking and may have the even surround of heat needed for baking or roasting.
Then there is the question of charcoal, gas, or electric? Portability becomes another question.
I bought the original charcoal Weber Kettle grill/smoker at the Base Exchange 45 years ago and I am still using it. Not as pretty as it once was, but nothing rotted through and just as functional as ever, for grilling, roasting, smoking but not useful for rotisserie and not portable for RVing. This one still sells for about $100, but you might be getting some accessory parts too, for various cooking methods.
My brother went through three "do everything" gas grills in the same 45 years, at successively higher prices (paid almost $2000 for his last one, all stainless steel). Parts eventually rusted through, needed regular repair or replacement, but not too expensive because most functional grill parts are generic.
For RVing or camping, I find portability to be an issue. If you want gas or electric, with some small smoker capability, and longevity, I recommend the Baby Q, it is built as tough as the kettle, comes in both gas and electric versions.
If you will do charcoal, the Weber Smokey Joe is a more portable kettle, same capabilities, just less capacity. But consider your storage space. What fits best in my underfloor are the little box grills with smoker lids. The Weber Go-Anywhere as a high end example, but there are cheap clones like Uniflame, charcoal or gas, for about half the price, almost cheap enough to be disposable.
For something that will last forever, there are cast iron grills in small box sizes, somewhat heavier than porcelain coated steel. If you want to just grill in the open, using charcoal, a hibachi costs about $30 in cast iron, $15 in steel, and packs into a small space.
One I can recommend against is the Coleman Camp Grill (at least three different versions including the Fold N Go) because it is too shallow, burner to grill, this causing uneven heat distribution in a not particularly useful pattern. I got it because it packs up about the size of a briefcase, but it just doesn't cook very well. This makes me shy about their larger (suitcase size) portables like the Roadtrip and NXT models, which are similarly shallow, burner to grill.
