I ordered a bunch of insulated coveralls and bib overall to compare.  I am 6'8" tall wear a 38 inseam.  Im hard to fit.  Here is my evaluation of some

Carhartt Men's Big & Tall Arctic Quilt Lined Duck Coveralls X01: I wasn't impressed with the construction of these or the fit.  They were baggy in the back and didn't fit as well as others.  The insulation wasn't as thick as the Carhartt Men's Arctic Quilt Lined Duck Bib Overalls R03.  They were high waters as well.  The inseam was only 32 I think.

Carhartt Men's Arctic Quilt Lined Duck Bib Overalls R03.  I liked those much better than the Carhartt coveralls above.  The insulation was much thicker.  But there were three issues 1) there was no insulation in the bib which made them colder 2) the attachment for the shoulder straps is really hard to hook and 3) the zipper on the legs only goes up to the knee.  This made them much harder to put on with shoes.  These Carhartts had 36" inseam that was great and fit the best but I decided not to get these for the reasons above.

Walls Men's Zero-Zone Duck Insulated Coverall: These fit the best of the coveralls I tried.  I liked some features of them but the zipper on the side didn't go all the way up which make it harder to put on with shoes on.  Also the insulation on the bottom of the leg didn't go all the way to the bottom.  The bottom 6" of the pants don't have insulation in them.  But in my opinion they were better than the Carhartts and the Polar King by Key Apparel Premium Insulated Bib Overall.

Polar King by Key Apparel Premium Insulated Bib Overall:  I liked the construction of the Polar King the best of all of them.  They have great pockets but the inseam of it was way too short.  It was only 31" even though it was a Large Tall.  I would say it is not a tall at all.  I wish the legs were longer and I would have purchased it.  The crotch was 1/2 way to my knees.

Key Apparel Men's Insulated Duck Coverall: I ordered this in the Large Tall.  The inseam is only 31 and gave me really high waters.  Other than that these were nice.  One button fell off right out of the bag.  Zipper goes up most of the way up the leg which makes them easier to put on.  Have cuffs in the sleave.

Dickies Men's Big-Tall Premium Insulated Duck Bib All:  I liked these the best.  They have zippers going on the legs that go from the waist all the way up or down the side which make them really easy to get on and off.  There is a zipper in the front which the Carhartts don't have.  They are also insulated in the bib and the back which make them warmer.  I wish they had more pockets but they work.  There is a reinforcement patch where you hook your tape measure on the pocket.  So I decided to go with Dickie Insulated Bib Overalls as they fit better with at least 34" inseams.  I am very happy with them.