Which NEMA 17 Stepper Motor for Titan?
The safest thing to do is to wait a month (it probably won't take that long anyway), and order the correct stepper motor from China, or pay more and locally source the 42BYGHW609.

The 42BYGHW609 is a commonly used stepper and it is best to keep all of the steppers matched - just for ease of calibration, matched performance/behaviour, and future maintainability.

Otherwise you need to match (at least) the torque, the inductance, the rated current and resistance of the coils, if not the physical size and the stepping angle. Which is not an impossible task, but a bit of a pain, TBH.

The time that you spend verifying the various steppers and then re-checking and worrying would be better spent ordering the correct one in the first place and waiting for it to arrive.

BTW, take a look at the RepRapWiki - Nema 17 page which lists suitable stepper motors.



As an aside, if this is your first purchase from China and are worried about reliability of service, then don't. I order everything from China, and haven't had a problem. In addition, if you order via eBay/PayPal you are financially protected if your order doesn't arrive (which does sometimes happen), or, alternatively, order from AliExpress, where I have never had something not arrive (if that makes sense)



I have just realised that you need an extruder replacement (and not a X/Y/Z stepper)... in which case, as towe states, either of your candidates is probably fine, although maybe over-torqued (slightly).

However, I, personally, would still replace the stepper with the same model that the 3D printer originally came with, but that is just my personal preference - unless you had found the 42BYGHW609 to be not strong enough, and you actually want to up the torque..?