I will use the block for barrel swaps changes on my 9mm and 45 acp uppers.

Brownells
http://www.brownells.com/gunsmith-tools-supplies/rifle-tools/bench-vise-blocks/ar-15-m16-upper-receiver-action-block-prod22385.aspx

DPMS
http://www.brownells.com/gunsmith-tools-supplies/rifle-tools/bench-vise-blocks/ar-15-ar-style-308-upper-receiver-block-prod17094.aspx

Also same question for the lower Brownells or DPMS

The brownells is really nice.

I went with this one: eBay

There are other auctions that just include the parts for the upper block, but I needed the lower block as well, and the dry-fire / cleaning inserts are nice to have. 40 bucks shipped isn't bad.

The main reason I went with the one I did is that I have heard that the clamshell style won't work with the Aero Precision COP upper (and maybe some billet uppers?). I don't trust the style that work on the takedown tabs, though the DPMS one you linked at least has a tab that protrudes into the upper to hopefully bear some of the torque. I don't trust torquing down a barrel with just the takedown tabs bearing the load.

Considering this setup also or part of it.  

Have you used it yet?  Thumbs up?  Hard to beat the price.

Thumbs up on the lower block, works great.
Thumbs up on the 'dry fire' block, works great and handy to have.
Haven't tried using the 'cleaning block' yet, but it does fit. Not sure how useful it will be.
Thumbs up so far on the upper block. I am waiting on my grease to fully torque down my barrel but the upper seems very stable in the blocks and I don't think I'll have any issues applying full torque amount to it with this setup.

It depends on what you're doing.

For torquing down a standard barrel nut or installing a muzzle device, I think the best solution is the Geissele Reaction Rod.

My favorite action blocks are the Block Worx Upper Vise Block and the Spike's Billet Upper Assembly Block -- both available from Spike's.

The Block Worx fixture is also good for applying torque to the barrel nut.  It is also useful for disassembling a particular kind of rail as well as cleaning.

eta: Reading is fundamental.  I didn't realize you needed them for a 9mm and .45cal upper. I don't think the reaction rod would work with those.

Don't know about better.   But for $27 shipped, this one works well.  

http://www.ebay.com/itm/ARMORERS-HEAVY-DUTY-UPPER-RECEIVER-VISE-BLOCK-TOOL-4-15-NON-S-C-A-R-H-D-P-E-/150992738649?pt=LH_DefaultDomain_0&hash=item2327de5959