One important note about the Alaskan package, if you care, or if it matters to you.
The Alaskan package comes with MT tires. These look great, BUT, GM de-rates tongue weight and towing compared to other tires. It is somewhere around 1200 pounds tongue weight (vs 1450 gas) and 12000 towing (vs 14500 gas). This will show up on the B pillar sticker.
These MT tires are used on other packages like the Z71 Sport, but that would fall out of your target price range anyways.
The GMC doesn't offer much, but one difference (if you care) is that GMC will have LED headlights/tail lights (mixed with some halogen), where the Chevy trucks would only have it for the cab markers and mirror lights until you step up to the LT Z71 Sport or LTZ. Otherwise, the GMC trucks are pricier without offering much more other than a different style.
As noted, they do package them different, some better, some worse.
Mechanically, and capability wise, they are the same. I have heard people argue that the GMC is a superior truck in terms of quality, but I have owned both over the years, and never saw a difference in quality, but everyone has different experiences, so your experience may as well.
Both really nice trucks, whichever you choose.