Most skate wheels (including skateboard and inline skates) are made of urethane.  It is a plastic material that is inexpensive and generally non-toxic to produce. Urethane varies in quality, typically communicated in its "rebound;" high-rebound urethane is thought of being of higher quality as the material will deform under stress and return to its original shape.  

Softer "outdoor" wheels are at the lower end of the durometer (78a ->85a).  Most people will prefer softer urethane wheels for outdoor skating since the squishiness of the material effectively absorbs shocks from the uneven surfaces.   

Harder "indoor" wheels are at the higher range of the durometer scale (95a+).  I use the harder urethane wheels for dance and short distance skating outdoors as they transfer my power efficiently and allow me to slide a little.

These wheels have the most consistent slip-grip ratios: 

• 0:100 on well-coated maple floors

• 0:100 on lightly coated maple floors

• 1:99 on uncoated maple floors

• 0:100 on sealed concrete floors

• 0:100on epoxy-coated concrete floors

• 5:95 on painted/porcelain tile

• 20:80 on sport court tile

Modern Vanathane is a remake material.  It has similar properties in terms of slide feel but their durability is clearly different due the absence of the "magic" ingredient, asbestos.  They are known to cone a lot faster.  The styles that appreciate the slip-grip properties of vanathane also use their edges a lot (NY/NJ-House style). The consistent use leads to the loss of edges, also known as coning.

Modern vanathane does get little pits and cracks really quickly compared to the vintage material which makes them more work to keep clean and slick.

They are 94-95a

There's a lot of good information out there on VV wheels.  The best resource out there seems to be Sk8Berlin and can be read here. They say that these wheels were the perfect balance between slip and grip for dance styles. I use them for my non-sliding dance, and they work well.  Being a porous material, they do pick up dust/dirt; because of that, I recommend cleaning them at least once every two or three sessions, so they stay grippy.

Vanguard vanathane wheels with no hub measure 55D
Vanguard vanathane wheels with a hub measure 60D

These wheels have consistent slip-grip ratios: 

• 15:85 on well-coated maple floors

• 15:85 on lightly coated maple floors

• 20:80 on uncoated maple floors

• 0:100 on sealed concrete floors

• 5:95 on epoxy-coated concrete floors

• 30:70 on painted/porcelain tile

• 25:75 on sport court tile

Fo-Mac wheels are hard clay wheels. Skaters that feel as urethane and vanathane wheels both grippy should probably start here.  Unlike thermoplastic wheels which can deform, FM wheels do not deform from pressure and will maintain their shape until ground down, chipped, or resurfaced. FM wheels were very common back in the day until vanathane made its debut, followed by urethane which sized the throne once the production of vanathane was banned.

These wheels have fairly consistent slip-grip ratios: 

• 45:55 on well-coated maple floors

• 45:55 on lightly coated maple floors

• 60:40 on uncoated maple floors

• 40:60 on sealed concrete floors

• 50:50 on epoxy-coated concrete floors

• 75:25 on painted concrete/porcelain tile

• 70:30 on sport court tile

Wooden wheels were a popular indoor wheel materials.  They are pretty slippery depending on the kind of wood they were made of and the surface quality. Wood wheels are extremely light when compared to other plastics, metal or fiberglass wheels.  Whether lightness is a useful feature when jumping on wood wheels is questionable is neither here nor there.  Wood wheels do have a limit to how much impact they can take before the fibers snap and the wheel breaks; we don't recommend jumping or stomping styles when using these wheels.  In terms of sliding these wheels are not as consistent but given favorable environments (smooth and not humid), can be incredible sliding candidates.  Being a natural porous material, they do pick up dust/dirt; because of that, I have to recommend cleaning them at least once every or every other session, so they stay grippy and more predictable. 

These wheels have inconsistent slip-grip ratios: 

• 50:50 on well-coated maple floors

• 45:55 on lightly coated maple floors

• 95:5 on uncoated maple floors

• 50:50 on sealed concrete floors

• 70:30 on epoxy-coated concrete floors

• 95:5 on painted concrete/porcelain tile

• 100:0 on sport court tile

Insert dinosaur joke here

I want to roll these at least once, just to suffer a little.

This list is ranked by slip:grip and fibers have the highest ratio that I've experienced.  Sliding styles use fiberglass wheels for their low-friction consistency across several floor surfaces.  The grippiest being sealed concrete floors which are still possible to slide on. These wheels are standard affair for the Cali Slide Style and feature prominently in my personal style, Freestyle Slide. While wheels harder than Urethane are squarely on the "slip:grip scale" and can be used to resolve slides, fibers are able to consistently slide with minimal effort.  Consequently, fibers can be challenging to skate in.  Skaters with fibers on cannot push off with high amounts of force as the wheels will simply slide. Likewise, spins and jumps which rely on using edges cannot be resolved easily at all.  Many jam skate dance moves and steps which rely on planting the feet and pushing off will not function as intended.  

These wheels have extremely consistent slip-grip ratios: 

• 95:5 on well-coated maple floors

• 100:0 on lightly coated maple floors

• 100:0 on uncoated maple floors

• 70:30 on sealed concrete floors

• 95:5 on epoxy-coated concrete floors

• 100:0 on painted concrete/porcelain tile

• 100:0 on sport court tile