Does it matter and can I download either one to perform the update?
It does not matter. If you are downloading then it's already an undated one.
All you need to do is, uninstall the previous one (
Make sure you have the wallet.dat files files in the wallet folder are saved in a different drive or you have the seeds saved somewhere else so that you can restore the wallets) and install (Windows Installer) the updated one. If you are planning to download Standalone Executable one then just move it to a drive instead of keeping it on the download folder and create a shortcut in your desktop then run it from there every time.
Not the first time people have to tell you this: Electrum does NOT (NOT NOT NOT) use wallet.dat files! Stop telling this to people... Electrum uses default_wallet without extention for the default wallet file.