Jenny, I found that thread, but I had thought there was one somewhere mentioning the "legacy" word that I wanted to review as that is what I really don't understand (if there will be some difference for me).
Legacy means support of older computer hardware and older operating systems:
https://filehippofy.com/software/antivirus/download-free-malwarebytes-2-2-1/MalwareBytes 2.2.1 supported back to Windows 2000
Windows 2000 / XP / Vista / Windows 7 / XP 64-bit / Vista 64-bit / Windows 7 64-bit / Windows 8 / Windows 8 64-bit / Windows 10 / Windows 10 64-bit
https://www.malwarebytes.com/pdf/guides/MBMRGuide.pdfMalwareBytes 2.5 supported back to Windows XP SP2
Windows 10 (32/64-bit), Windows 8.1 (32/64-bit), Windows 8 (32/64-bit), Windows 7 (32/64-bit), Windows Vista (32/64-bit), Windows XP (Service Pack 2 or later, 32-bit only)
CPU: 800 MHz or faster
RAM: 256 MB (512 MB or more recommended)
https://www.malwarebytes.com/pdf/guides/Malwarebytes-3.0-User-Guide.pdfMalwareBytes 3.0 supported back to Windows XP SP 3 or Vista SP 1
Windows 10 (32/64-bit), Windows 8.1 (32/64-bit), Windows 8 (32/64-bit), Windows 7 (32/64-bit), Windows Vista (Service Pack 1 or later, 32/64-bit), Windows XP (Service Pack 3 or later, 32-bit only)
CPU: 800 MHz or faster
RAM: 2048 MB (64-bit OS), 1024 MB (32-bit OS, except 256 MB for Windows XP)
So with newer versions they drop support of an older version of Windows and sometimes increase requirements.
MalwareBytes 2.5 had no support for Windows 2000
MalwareBytes 3.0 requires the latest Service Packs for Vista and XP as well as requiring more memory for Vista and later.
If you have Windows 7 or later and a fairly recent computer (not 10 years old), dropping support of legacy products shouldn't be an issue. They add support for newer hardware and new versions of Windows.
If the computer has XP, you really shouldn't take it out on the Internet unless you're an expert in computer security and know how to lock down Windows XP to prevent infection.