explain electronic speed controller....

[autonm]

after about a 15 year absence I got back in 1/10 buggies about 3 months ago.

I bought a B44 along with a LOSI XCELORIN S 6.5T BRUSHLESS COMBO for around £115.....cheap entry - but good enough to get me going.

Im now looking into buying a more improved motor - possibly a LRP X12 for around £80-£100.

Now I can understand that a better motor would give me faster acceleration/speed etc etc .... but can anyone explain the benefits of buying a £100+ speed controller?

I dont understand what in a speed controller differeatiates a £60 one to a £150 one?

thanks for any explanations