I voted 'Other'. Proper sand for menages and topped with PVC granules - its what I have. Its 13 years old, always rides perfectly, never freezes. Its an outdoor school and has been usable all winter (as it was every other winter).
I do look after it though, I harrow it regularly and had to do a top up of PVC granules last year as they were getting a bit sparce.
Mine is sand and rubber, it took a few months to bed in, but now it rides beautifully, drains really well, doesnt get too dusty in the summer or freeze in the winter and is easy to maintain.
We have a sand and rubber surface outside and a waxed fibre surface indoors. They ride very differently and some horses prefer one over the other. The sand and rubber allows them to dig into the surface and push off it whereas the waxed surface they don't dig into it at all and just ping off the surface. The benefit of the waxed surface is its dust free so great for horses with respiratory issues but it took my horse a while to get used to riding on it. However I would say I far prefer the waxed surface over the sand and rubber surface now.
Be very very careful with rubber surfaces. they are not all they are crakced up to be. Lovely to ride on, but there is far more to consider . . . . .
Rubber contains toxic substances which leak out into the water table and surrounding area.
Rubber degrades, and when it needs removing and replacing, you will not be able to dispose of it in any way whatsoever. You'll be stuck with a broken down surface. There are VERY strict laws concerning the disposal of rubber. Disposing of tyres is now a huge problem, and we are being made mugs of by being sold chopped up rubber to ride on.
I looked into this in great depth when I built our arena, and was horrified with what I learnt about rubber surfaces. I'm not a tree hugging eco-warrior hippy type, but i don't want to cause any damage to the environment if I can help it.
Furthermore, planning was touch and go with the council, and I figured that if i kept it as natural as poss, they would be happier. It paid off, as i got permission. I used wood chip (not recucled). It has its drawbacks, but i just potter around doing a bit of dressage, so it suited me fine.
We have sand and rubber outside put down 18 years ago had one top up in that time and is absolutely brilliant, never frozen, never has a puddle on it, no sign of rubber even remotely breaking down. We have 20 horses a day on it.
We have gel inside, brilliant, low maintanence, never needs watering horses love it however I would not have this outside.
My trainer had gel outside on hers and she said that in the very hot weather the gel got really hot and burnt her dogs paws and after a few years it went like pudding in the wet weather.