Onecnc will post G code for Mill and Lathe. Mill and Lathe are two different packages though. I have used everything from Meshcam, VisualMill to Mastercam. Onecnc XR5 Pro works great and I have been reasonably happy with it the last couple years.
The biggest pro is support without annual maintenance fees. The software is easy to use but like every piece I evaluated or used--they all require some work around for some operations. Whether it drives you nuts depends on your parts and how you approach them.
Since you already have Solidworks I would advise you to try out a free copy of HSMWorks Xpress before you do anything else. Solidworks/HSMworks seems to be the direction that most move after a few years of experience. From what I understand you can't beat the power for 2.5D CAM and the price is right.
Cons - OneCNC is not integrated into SolidWorks. OneCNC likely costs more. Some people may actually prefer a menu-driven system rather than a wizard-driven system (though I believe BobCAM uses wizards now?)
Pros - I actually prefer the look and feel of OneCNC. I programmed parts in about 10 minutes without even reading any manual (XR3). I have XR4 Mill Expert and the CAD side leaves a little to be desired, but works for my needs; XR6 is leaps and bounds better (though I don't have it yet.) BobCAM has added more machining strategies that I'd like, but so has OneCNC. No maintenance fees are a plus, and the phone and forum support are great. The best part is you won't have to deal with the incessant nagging from BobCAM salespeople, and I've been through it and it is frankly horrible.
I use Mach3, though I cannot remember which post-processor I used. I also use USBCNC from EdingCNC and can post gcode with the FANUC 21 post processor.
I used Bobcad for a while then switched to XR4 then XR5. Truth is, Bobcad is cheap basic entry level software and fits well for a hobbyist or someone who isn't concerned with time and frustrations. If quality and advanced machining processes are important, one needs to step up to more powerful, machinist duty and intuitive software. OneCNC works and works well. I can't say enough about Patrick at OneCNC West. If you have any questions, give this guy a call.No sales tactics, pressure, just honest free advice.