Which 2011 MacBook Pro is better?

those models have replaceable RAM DIMMS, almost the last models with that feature.

16 GB is US$26.99 plus shipping from Illinois, USA or your local Mac-Friendly vendor:

https://eshop.macsales.com/shop/memory/Apple_MacBook_MacBook_Pro/Upgrade/DDR3_1333MHz_SDRAM

16GB with a 2.0GHz processor is better.

you can't run ANY browser on 10.6.8

SSL to TLS:

In 2015, researchers discovered that Secure Socket Layer (SSL) Internet encryption was not nearly as secure as was thought, and needed to be replaced. Internet encryption quickly moved to Transport Layer Security (TLS) which was rapidly deployed across the Internet. Over time, sites tightened requirements for what was acceptable for encryption.

Apple issued Safari version 9 in 10.11 El Capitan version of MacOS, which included TLS encryption. It was later provided by Security Update into the two previous versions of MacOS. 10.10 Yosemite and 10.9 Mavericks, PROVIDED you applied all available software updates.

MacOS versions older than those can not make a lot of secure [httpS:] connections on the Internet, because by todays standards, your proffered SSL encryption is considered inadequate.

only the 15-in and 17-in 2010 models have a HARD Limit of 8 GB.

2011 CAN be expanded to 16GB, PROVIDED you obtain EXACTLY the right modules from a Mac-Centric Vendor who can support you if it does not work.

Rather than paying money for stuff that is already obsolete, consider running a Virtual Machine inside a more advanced Mac.

you could also consider what I did:

I run an older macOS inside a Virtual Machine on a newer Mac.

That model MacBook Pro only supported a maximum of 8 GB RAM, so there's that.

They are both relics, but you knew that already.

The difference in CPU clock speed is insignificant.

FWIW, I would rethink why I need a vintage/obsolete computer. I would not get either. I would get a newer still supported model that will get updates for some time.

Why the need for such an old computer?

You need the Antique Roadshow website, not this one ;-)

I assume you've got a good reason for needing such an old OS but you do know that the likelihood of finding a browser that will work with most of today's websites is virtually zero, don't you?

The 16 GB configuration is nonstandard. Apple never sold that model Mac with 16 GB. That configuration is not supported by Apple. Unexpected things can occur with unsupported configurations. Furthermore, without its original RAM (4 GB DIMMs) you won't be able to replace it in the event you suspect a RAM problem.

It's a moot point though, since Apple no longer supports that Mac anyway.

The plot thickens: Bizarre behavior of older MacBook Pro ... - Apple Community

I use Apple's published specifications. Anything else and you're on your own.