Hi. Updates are normally devised to bridge security flaws the manufacturer came to be aware of, extend batter life, improved speed and may have additional features or tweaks. While of cause every firmware update has an inherent risk of a boot loop or soft brick, every update ever rolled out is needful. Therefor yes I suggest you go for the update. Fortunately, there is an official ROM availablet for the Vivo Y51 incase anything goes wrong during or after the update.