Its a tough comparison, but first off don't go with a Viper 125 - 60 second average output is likely closer to 95-115mW. I would suggest going with novalasers - they have a good reputation and would probably deliver at least >123mW on a 60 sec average.
The DX NewWish laser really is a toss up. Its a fraction of the cost, and for good reason. The Viper/novalasers x series lasers are tried and true, high quality units. The DX are.. not. I'm not too sure about power outputs on the DX though. I've heard claims of getting peak green ratings ~200mW with the best batts, but not just because of leaking IR, but also because of stability issues I wouldn't expect the 60 second average to be as impressive. That said, I wouldn't be surprised if you can pull 125mW of green out of a DX on a 60 sec avg, but unfortunately I've only owned the 100mW units so I can't tell you for sure.
Generally though, if you want a good, solid, quality greenie, go with the nova x series. If you mind taking a bit of a gamble on a crappier greenie, you may save hundreds of dollars and get the same raw output with a DX/NewWish.