I prefer a cooktop/wall oven combo. I like not bending over to use the oven or even just to look in. I like not standing in front of the warm oven when I'm cooking. You can have a 36" cooktop with a 30" wall oven, allowing the space under the cooktop to be used for drawers.

The benefit people mention about a range is that the hood over the stove works for the oven, too.

Cost is a significant factor. Separate items will probably end up costing 3Xs the cost of a range.

Now that i've switched to an induction cooktop with a separate wall oven with speed oven/micro above it I would not go back to a range.

A couple of factors others haven't mentioned yet:

Consider the square footage of your kitchen. I had a small kitchen and converted from cooktop/wall-oven to range. Yes, the wall oven preheated faster and was easier to pop things in and out of because you don't have to bend over as much, but I have a pretty small kitchen. The counter space I gained by getting rid of the wall oven is priceless and is used every day, whether I am baking or not.

My range oven is also larger than my old wall oven, which allows me to bake batches of Christmas cookies more quickly. So, consider the size of oven you need as well. I love being able to use a caterer's "half sheet" pan in my range oven.