NGP mechanism vs the simple carbocation mechanism
From Clayden (Chapter 37 Rearrangements page 976):


  Intramolecular reactions (including participation of a neighbouring group) that give three-, 
  five-, or six-membered rings are usually faster than intermolecular reactions.    


It also gives the exact same example as your question:


  


Notice that both products are given to be exactly 50% each. 

NGP is very often faster than bimolecular reactions as for the latter to take place two molecules have to collide first.   

1:1 ratio can be attributed to the fact that in NGP the transition state involves loss of aromaticity BUT NGP supports the ionization of the starting material. 

There are a lot of examples  this one reaction isn't a black swan. Interested readers may see chapter 36: Participation, rearrangement and fragmentation in Clayden to find more details and examples.