I started with Fun Factory, and I loved their designs so much that I didn't see the point to get something from another company. The special thing with Fun Factory is that there is a drag on the silicone and they sometimes mix that up with a smoother texture. However, now that I've tried silicone from Regular Vixen, Vixskin and Tantus... I gotta say that they all have something unique. I've only touched the silicone from the Lelo Ina, and I do not believe it represents well a pure silicone toy from that company, so I won't include it, but:
Tantus is super glossy and is the firmest.
Fun Factory is matte and second in line with firmness.
Regular Vixen is smooth enough to shine and is still a little bit more flexible/soft than the previous two.
Vixskin is well... so realistic, that handling it is a turn on.