Quote from Maverickz:
The difference is positive Vega vs negative Vega. They are almost identical in terms of Delta but NOT Vega.
you have it messed up.
vertical spreads with the same strikes HAS the same vega. wheather a vertical spread is positive or negative vega depends where the spot is - not if you build it from puts or calls...
p.s. as i already mentioned, just use put-call parity and there you have the result - it is the same thing.
