Combined, the long call and the synthetic long put (long call plus short
stock) creates a synthetic straddle. A long synthetic straddle could have
similarly been constructed with a long put and a long synthetic call (long
put plus long stock). Furthermore, a short synthetic straddle could be
created by selling an option with its synthetic pair.
Notice the similarities between the greeks of the two positions. The
synthetic straddle functions about the same as a conventional straddle.
Because the delta and gamma are nearly the same, the up-and-down risk is
nearly the same. Time and volatility likewise affect the two trades about the
same. The only real difference is that the synthetic straddle might require a
bit more cash up front, because it requires buying or shorting the stock. In
practice, straddles will typically be traded in accounts with retail portfolio
margining or professional margin requirements (which can be similar to
retail portfolio margining). So the cost of the long stock or margin for short
stock is comparatively small.