Please base your answers, solely on what the park offers...

Edit : RCT3X - Help Hjem-is decide which park is the best to go to, Thorpe Park, or Alton Towers. Feel free to state reasons for your choice etc...

Sorry I have no idea??

I would say Alton Towers, for the unique rollercoasters!

Air - 1st Flying Coaster, nice smooth ride
Nemesis - Great Intense Inverted Coaster
Oblivion - Vertical Drop Coaster. Fastest coaster in the park
RITA - Launched Coaster with a basic, but great layout!
Spinball Wizzer - Cool Spinning coaster.

Also, some other great attractions such as HEX, which is very well themed ride, based in the towers. I wont give anymore away.

Charlie and the Chocolate Factory coming this year will be a very well themed ride, with several unique features includind a 360 degree, glass elevator with views of the chocolate factory.

MORE

Alton Towers!
better rides, more rides, bigger, much more of an atmosphere, plus it has the origional nemesis!

Or possibly Thorpe Park for its sheer amount of rides...

Collosus - Worlds ONLY 10 inversions rollercoaster
Stealth - Brand new to 2006, fastest/tallest launched coaster in europe
Nemesis Inferno - Not the original Nemesis, but top draw nonetheless
X - Pitch black, backwards rollerocaster, very dis-orientating

Rush - Worlds Largest Giant Swing
Slammer - Only skyswat ride outside of the US
Detonator - 100ft freefall drop
Vortex - AMG Afterburner, this ride packs one hell of a punch.
Samurai - A ride with alot of G,s
Tidal wave - Speaks for itself
Loggers leap - Ageing waterflume ride, but still great.

Alton has more coasters, but Thorpe has better Thrill rides