If you're going with the Diamondback, try this: https://slickdeals.net/f/9796487-diamondback-and-raleigh-bikes-up-to-57-off-corporate-bicycle-stores
I used this method to get my Release 3 for $2300 (corporate code + sale price), which usually sells for $3900. The only downside is getting the right size and assembling the bike since it's being shipped vs buying from a shop. Assembly was incredibly easy though (installing the dropper post, attaching the handlebars, installing the front wheel and pedals, etc.).
Since you're looking at the Release 2, with the discount it might be worth bumping up to the 3 to get the upgraded drivetrain and suspension.
I can't speak to the two Giants you're looking at, but I'm loving the Release 3. It was my first major mountain bike purchase/upgrade since first getting into riding 15 years ago. I've taken it to Saw Wee Kee a few times now (just got the bike a month ago), and it is a beast on the trails. It doesn't climb nearly as well as the hard tails I've ridden, but it excels at every other aspect of trail riding. And like others have said about dropper posts, once you ride with a dropper, you'll wonder how you've ever lived without one. By far one of my favorite features on the bike.
Hope that helps!