First things first, I'm reviewing the European pant here. Not sure if there is any difference between it and the pants sold in US, so I am mentioning it anyway.
(These come with both knee and hip armor -- CE level one -- that is from the Forcetech series.)

The second thing I want to say is that, for me, these run true to size. I'm between a 2XL and a 3XL, based on the size chart.

I ordered a 3XL and it fits me a tad large. I could have been fine in a 2XL as well, as I do have to cinch the 3XL down a bit at the waist. They are comfortable on the bike though.

I don't know why Revzilla recommends bumping up two full sizes, but I really think you should stick to the size chart. If you look at the video, you'll see Juice has the waist adjuster cinched all the way. And they look a bit baggy on him. Anyway...

Now, as far as comfort and protection goes, I find that these pants are really nice in terms of warmth during the cold season.
They keep me warm, with the waterproof liner inside and a base layer, in temperatures around five degrees Celsius. I never felt like I was cold with them on my naked bike.

Protection-wise, I like that there is hip armor in them but I wish the knee armor would go down a bit more down the shin. The hip armor is massive, it covers a huge area.

There's lots of adjustability at the knee for the armor, but the elastic panels are not as wide or tall as I'd like them to be. The video review mentions this, and I have to agree.

Ventilation wise, there are two zippers on the side, which I am not sure how well they will work during summer, but I think they will let some air in for sure. A zipper at the front would probably be more effective.

Keeping the price in mind, I think that these offer a lot of bang for the buck. Spidi does nice stuff, and I have another jacket of theirs so my outfit at least has matching logos on it :).

Something else worth noting is that mine came with a full zipper, so you can remove half and saw it to your jacket.

Keep in mind that, if you plan on going Spidi for the jacket as well, only a couple of Spidi's jackets have jacket-to-pants connecting zippers. Their all-around good stuff, like the 4Season, does not. There are crotch straps, but that is all.

I wear a 50"-51" pants so, following the instructions, I ordered two size bigger, so according to the chart a 4x or 5x would fit me and I ordered a 7x. Not even close. It was labeled 7x but no way these things are 55". Seem like a good quality product but I can't use it. I think if you got a pair that fit they would be fine but do not believe the size chart.