BER for OFDM-QPSK over Rayleigh Channel
w = conv(u,v) returns the convolution of vectors u and v. If u and v
are vectors of polynomial coefficients, convolving them is equivalent
to multiplying the two polynomials. (from MATLAB documentation)

Both expressions are correct. In 2., whenever an addend of a convolution operation calls randn in a convolution computation procedure, the callee returns new values for both real and imaginary parts of h.