Pumpkin is just another kind of squash.
True, as far as it goes, Grace. But "pumpkin" is merely part of the common name of certain squashes. There is no way to differentiate them, taxinomically, from other hard-shelled squashes. Indeed, early European settlers called all hard-shelled squashes "pompions."
Here comes the lecture, so you can skip this part: There are six (well, now seven---but that's a different story) species of domesticated squash, four of which are commonly grown in North America. All four of them have varieties commonly called "pumpkin." Yet, there are vast visual, textual, and flavor differences between these pumpkins. We've been socialized into thinking of pumpkins as generally round, orange-skined, orange-fleshed squashes. Taken collectively, however, that's the least usual shape and color. For instance, the most popular pie pumpkin among commercial pie makers is the Long Island Cheese pumpkin. This one is tan skinned, and flattened----looks more like a light-brown tire than a ball. Of late, white pumpkins are becoming popular (although they've been around for centuries). Unfortunately, the ones generally available are more like Jack O'Lantern pumpkins, when it comes to texture and taste. On the other hand, the White Boer, from South Africa, is considered one of the best culinary pumpkins in the world.
Because of this, the flesh of any winter squash can legally be called pumpkin. From an efficiency point of view, for commercial canning, you want a large, firm-fleshed, orange squash, hopefully with a high sugar count. This is why Hubbard and Cushaw are used. While less sweet than, say, Butternut, their size and shapes lend themselves to easier processing.
Until recently, it was hard to find pie pumpkins in regular markets. Although this has changed, somewhat, the past few years they are still often hard to come by. So, for home-use, rather than choose a Jack O'Lantern, which has a fibrous and watery texture, it's better to choose an alternative squash that meets your actual needs. Most often that would be butternut, because it's commonly available, and is sold in realistic sizes. It's one thing to prep a 2-3 lb Butternut, another thing to play with a 30-lb Hubbard. In theory, you could even use Acorn squash. Unfortunately, they've been hybridized to the point where the flesh is white (it was originally orange), and the sugar content low. Or, just do what most of our Mama's did, and go with canned pumpkin.
There is a difference in mouth feel.
Are you saying a difference between pie pumpkins and Jack O'Lanterns, ChefRoss? Or between fresh pumpkin and canned?
If the former, you're absolutely correct. If the latter, I believe any difference in mouth feel is in your mind rather than in your mouth.
I, too, grow my own pumpkins and other squashes. Don't fool myself for a minute that I could detect any difference between them and canned in either sweet or savory dishes. Nor do I believe you could, either, in a blind taste test.