If both ITM at expiration, they will be a wash. You better be sure they are going to be ITM, though. After hours action can change your position as well. Also, you need to be careful on spreads if you do not have sufficient funds. I'm assuming you have a margin account since you are trading spreads. Not sure about other brokers, but IB has some pretty draconian liquidation policies. You need to keep a close eye on your positions on expiration day if you are near to margin limits. Even if you have no intent on holding the trade thru expiration, IB doesn't know that. They can liquidate your ITM positions in ways you don't anticipate to bring your margin back in line. Typically this happens up to 2-3 hours prior to close (their discretion).
Also, it's a misnomer that spreads are "safe" and they are not just "set-and-forget" trades due to the possibility of assignment (European style options like XSP/SPX are more forgiving).