Macbook Pro 13-inch, Mid 2012, Hardware upgrade?

It will since it won't be accessing so frequently the HDD (RAM) and if it does it will access the SSD, which is a lot faster than a HDD. This applies to MacBook Pros as well to Windows laptops. So you will buying 2 years and update the OS if you have to no because you want to. New software requires more CPU power, more memory and more disk space (this applies to every piece of hardware - iPhone/Android, MacBooks/Laptops and desktops). I hope you had upgraded your device by now.
SSD vs HDD performance:
https://www.pcworld.com/article/2048120/benchmarks-dont-lie-ssd-upgrades-deliver -huge-performance-gains.html

Here's how to install new memory: https://support.apple.com/en-us/HT201165

Here's how to install you SSD: Upgrading Your MacBook Pro with a Solid State Drive

More info on installing SSD: How to Replace Your MacBook Pro's Hard Drive with an SSD

I wouldn't say there's necessarily any best RAM other than one that's known to be compatible. In that case Crucial is the only one that's really from a 1st tier memory manufacturer (Micron), and they have kits that they guarantee to be Mac-compatible. Other 1st tier manufacturers are Nanya, SK Hynix, and Samsung. There might be some Elpida modules out there too although the company is effectively out of business (acquired by Micron).

SSD is kind of a toughie too since most are going to be limited in performance by the SATA III interface speed. You'll find that the speeds are pretty much about the same across the board for any newer SATA SSDs. I personally like the ones from the actual flash memory makers, but that's up to you. That would include Samsung, SanDisk/WD, Intel, SK Hynix, Toshiba (OCZ), Micron (Crucial), etc.

This is one I have, where the 512 GB version is exclusive to Best Buy. If you're not in the United States, then there are probably other places you can get one. I think it's a pretty good value. Right now it says sold out, but that might not be the case at a store.

https://www.bestbuy.com/site/sandisk-ultra-512gb-internal-sata-solid-state-drive -for-laptops/5969506.p?skuId=5969506

if you are running Yosemite 10.10 or later in 4GB of RAM or less with a Rotating Hard drive, you are stuck in a rut. Appropriately-responsive operation requires MORE than 4GB of RAM for that and later versions of MacOS. Getting to the next increment in RAM will get you out of that Rut. It is definitely worth doing.

Beyond that, more RAM is a diminishing return, and does not translate directly to more speed.

I have the very same MBP and I upgraded my RAM and hard drive to an SSD as soon as I bought it (I never cared for the super slow 5400 rpm drive in these machines because it is really slow and 4 GB RAM just doesn't do it for the new OS versions). So, I got both the RAM and an SSD from OWC (macsales.com) one of the two most recommended vendors here; they are Mac centric and their RAM is specifically for the MAC model you own. They also have great how-to install videos.

And, my MBP is very fast.

https://eshop.macsales.com/shop/memory/Apple_MacBook_MacBook_Pro/Upgrade/DDR3_16 00MHz_SDRAM

https://eshop.macsales.com/shop/ssd/owc/macbook-pro/2012

MacBook Pro Installation Video at MacSales.com

I have the same MBP upgraded with 16gb. ram and 500gb. SSD.

Works great now. Performs very good. Better than new.

I have it setup with dual boot boot camp Sierra/Win-10-Pro

Works great in both Operating systems.

Has been working great for 3 years now and I dont mess with it any more.

Should be good for 5-7 more years.

8gb of ram is fine for everyday use.

16gb if you plan on editing video.

256gb SSD is okay.

OSX with many many apps will only use up about 90gb.

Larger disks if you plan on storing allot of music and videos.

500gb if you plan on Dual boot boot camp OSX/Winows ( 2x 256gb. partitions ).

Get a NEW battery if your battery cycle count is above 900

Best to Max out your MBP and never mess with it again.

Use only Approved components. OWC.com

I use Crucial brand ram and SSD

OWC battery.

Upgrades for MacBook Pro (2.50 GHz, 13-inch, Mid 2012)

Here is my post on the benchmark performance improvements to expect

after hardware upgrades.

( MBP-13 ) Win-10 performs better than OS-X