I have found for nose and balance canned seems to work best for me. The biggest mistake I've seen most brewers make is that they use regular old giant pumpkins. If you want to use real pumpkin use "pie pumpkin" tiny little things that are sweeter and easier to process. The canned is ready to go, smells great and it seems to me the sugars are easily reached by the yeast and it ferments out cleaner without as much pectin haze. This is just my opinion of course
Also - even if using canned pumpkin, make sure to roast it in your oven @350F for 30-60 minutes before you use it! This helps caramelize some of the sugars in the pumpkin, which makes the pumpkin a little less fermentable, making sure that some of the pumpkin flavor will be left in your finished product!
I was wondering the same thing. After tooo much research it all comes down to what you want your beer to taste like. I just used the canned pumpkin and concentrated on the spice profile.