I haven't seen much of the Collins chip... i have heard it mentioned before tho... i don't know much about the specs of it.
Autodelta do a re-map of the origional chip, But these are only for the 156's and 147's. The 155's they only offer replacement chips... the thing is though... i think these are just origional chips that have alreday been re-mapped... just swap it over... and it's looks like standard. (i had seen that somehwere on one of the previous discussions) But, it only adds about 7/8bhp (using a 2.0 16v TS) compared to the squadra which adds 13bhp... not much difference i know... but when the Squadra chip is £145... that's a fair chunk cheaper than the auto delta chip! (£235 - for the 16v cars - £199 for the 8v & V6 - £464 for the Q4)
Camparing these two main chips... i went for the Squadra... they were a cheaper and had better power gains... Apart from the extra few BHP the squadra adds a bag load more of torque too (20Nm) and generally makes the car more responsive and more fun to drive.
Both of these people also were a DIY job... the same risks were involved.
Dunno if this helps your decision at all.