Ok first, I think Highfidelity, as an open platform, is the better solution for a 3D internet. In this role is it sure interesting for commercial users. But I think, it is not an alternative to the second life user. Why?
The second life user are used to it edit freely their avatars. They can edit the skin, the shape, the tattoos and the texture clothes. Ok, texture clothes are not state of art, but it is not unimportant. Par example: you have boots and pants from different manufactures. A mesh pants is problematic with the boots. You can better fit the outfit with boots and a texture pants. In Highfidelity the only one possibility is attach or detach a mesh object.
Does Highfidelity underestimate how important editable avatars are? The next fact leads to the next problem. If you want edit your avatar, then you need an inventory. A normal user will not have an own server, and so he does not have an inventory. He can use only finished avatars. For solutions of third part enterprises is the avatar API not enough.
You would can rent an inventar place, or you can use a git hub. But i think, this are not alternatives for a normal user. Git hub is to difficult, and by second life they do not know it to pay for the core features.
The marktplace is not without problems too. If you want use the marktplace you need an own server. Only the urls get the customer, the content is of your server. The own server caused costs. In this case I can not sell objects, I should rent my objects, and this is not a way, but in Highfidelity the avatars has not an inventory.
I do not know Sansar. But if it has all the core features of second life and it is state of the art, in this case I fear, a second life user go to Sansar and not to Highfideltiy.
Is that wrong? What is your opinion?