It's definitely SANDBOX and MANA for now because there already many big brand invest on those metaverse and the project also looks promising and developing progress is also there. Eventhough metaverse projects is still early and there will be a lot of improvement once it launched, the concept of metaverse is already make a lot of people interest by imagine it how it will be when it's on perfect form.
They are currently the big players for sure, but this doesn't necessarily mean they are going to stay on top. In the crypto space many formely big currencies are now not worth much anymore and I could imagine MANA and SAND going their way. It is worth to invest into them now, but one needs to constantly monitor whether competitors appear that could take over the crown.