Sorry for the essay to come. Recently bought a 2nd hand Boardman comp for my 100mile bike ride for charity. Ive loved training and want to get into it more. Ive seen this defy advanced 3 2016 for £919 from pedal on. Ive been advised the 105 shimano groupset. However this is the tiagra. Will there be a massive difference between the 2 groupsets. Next one for me is 1500 with the ultegra or 105. What shall i do??