If you have two P30s, I would feel good about trading one for the Sig. If you think you would regret it at any point later, don't.
I'm curious how you have a SRT in an HK pistol. And if so, how comparable the HK is to a Sig. Sigs traditionally have much better triggers than HKs. I shot a P229 (normal) against a P30 and, while I preferred the P30 due to overall ergonomics, have to admit the Sig trigger is nicer.
I also prefer the decocker location on the Sig to the P30. If it were an HK45 with the lever, it wouldn't matter as much, but the Sig's decocker is nice.
If it were one or the other, I'd go HK. But if its one of each or two HKs, I'd go with one of each