It really is up to each individual's wants, and no one can give you an answer, except you. We can all share our own experiences, but in the end, the choice is yours.
We started tent camping and started with Coleman camp stoves and cooking over a campfire. . We then got our first pop-up and it came with a stove that could be used inside, or mounted on the wall outside. We still continued using the Coleman camp stove and the outside hanging stove and never fixed meals inside. We still fixed a lot of meals over the campfire. By now, we were getting pretty tired of cleaning soot off of all the pots and pans. And all the black from campfires.
Fast forward 6 more years and we got our first travel trailer. We didn't want to cook inside the camper, splatter grease and smell it up, so we continued using the Coleman camp stove outside.
Second trailer, same thing. By now, we'd moved to both the Coleman camp stove and electric frying pans, and then we switched to electric flat griddles. By now, we were completely done with cooking over a camp fire, dealing with black fire soot all the time and cleaning a tripod and grates.
Then we got our 3rd travel trailer and we now have 2 flat electric griddles and an electric skillet. We got rid of the 2 Coleman stoves we had and all the paraphernalia we had for it. We no longer do meals over a campfire. Our current camper has an outside flip down gas stove and a small sink with hot and cold water.
With all the variations we have now, we still fix meals outside. We really like the outside flip down gas stove and we use the outside water a lot, especially for washing dishes.
We've been looking at fifth wheels and considered the outside kitchen. But the kitchen seems to take a lot of space, is fixed in one spot (and usually comes with a place for a television).
Actually, we like the ability to move the griddles anywhere. If the sun is beating down at just the wrong angle, you're dealing with intense heat standing over a stove. If the sun is glaring in just the wrong direction, it's impossible to see the screen on the television. And not to mention if it starts raining or the wind kicks up a lot. Having the stove, griddles, BBQ, or whatever, fixed in a permanent position can be very frustrating. Keeping everything mobile provides a lot of variety for any situation.
A couple times we were camped on a hill. We absolutely could not use the outside flip down stove because it came to about the height of our shoulders, as we were on a hill on that side. And yes, that first step out the door was a doosie too! If we were not portable with the electric griddles, we'd be forced to use the stove inside.
Some folks really, really like the outside kitchens. Some do not. For us, it's just not a practical feature for our style of camping. Especially, since we have an outside fire pit at home and we are able to drag all that stuff to the fire pit and set it all up independently. We still have the campfire tripod and all those grates and the cast iron pots and pans and all of that. But when the day is done, at home, I can just spray it down with oven cleaner and hose it off in my own yard. In a campground, you can't do that.
We enjoy outside cooking and have learned to use any variety of heat sources. In our camper, we always have the resources to cook with electric inside and outside, propane, inside and outside, and over a fire if push comes to real shove. So we still carry a couple pots that can handle a direct fire.
The choice is yours, and you may find a fixed kitchen to be either restrictive or absolutely heaven sent! It really does depend upon your intended use.
For us, we need mobility.