If you file I-140 and I-485 concurrently then your I-485 will have earlier PD.
You may get EAD, AP (if you need early for you and your spouse)
If you want to use AC21 in future it may be good that I-485 was filed when I-140 filed and if I-140 approved and I-485 crosses 180 days you may use AC21, read the recent 180 days AC21 MEMO in other thread