It's not "necessary" but would be nice. Larger SSDs are also faster than smaller ones but that all depends how much you plan on put on it. You can count on at least 10 GB free necessary for windows operation and about that much for SSD's health sake, all on top of 120GB drive actually has 111GB after formatting, W10 takes about 20GB for installation and you are actually left with only 50 - 60 GB for your programs.