cropped or full frame for portraits/modeling?

Would you rather have a full frame camera or a cropped sensor when shooing glamour/modeling/portr​ait shots... just out of curiosity and why?

Full frame. For the proposed subject matter, there is no need whatsoever to crop down the image. This means a larger sensor will provide better resolution for all scenarios (due to less total enlargement from sensor to print).

I would only use a 1.6X body if I needed to save cost.

Obviously you can get stellar results either way. FF offers a little more dof control and technically uses EF lenses the way they were designed.
If you do work that involves oof highlights, the crop mirror box will cause a chopped effect on the oof highlights, esp when using a very wide aperture, such as the 85 1.2 wide open or close to it. Not a big deal really, but something that is interesting to note anyway.

A larger format entails the need for less final magnification. Less final magnification means that more total resolution is available. Larger format also entails the use of longer FL, and as a result the larger format also has better separation of subject from background for better subject isolation. Now having said that, I will state that this is ALWAYS true, and so really if you are going to shoot portraits you really need to get a digital Hasselblad or other medium format camera with digital back, which will merely set you back USD $30k, or only $10k if you settle for a Mamiya 645AFD !

And if you are not ready to make such an investment, APS-C is darned good enough!

My 5D does a fantastic job with detail. I have been shooting portraits with it for over a year and have not been disappointed once. If I had the money, I'd get another one.

thanks for the answers guys. appreciate the gained knowledge

Same difference imo.... it is more the lens I am using that concerns me the most.

I get great results from either but I do really like my 5d....

hell, for modeling stuff i'de rather use a 5d than my MKIII any day... so much nicer results

No preference.

While the FF cameras are claimed to provide superior resolution and detail I believe that the crop cameras can do the same, given that they both use a lens that is capable of providing enough resolving power for the sensor.

The key issue is the availability of lenses for each format. For FF you have the widely coveted 85mm f/1.2L II. If you want to achieve approximately the same field of view on a 1.6X crop system then you may need to go for the 50mm f/1.2L. At this time there will be a lot of debate as to which is better.

And if you want 135mm field of view, there is the legendary 135mm f/2L for the FF system. On a 1.6X cropper you will need to use an 85mm f/1.2L II (85mm f/1.8 would work also at the cost of reduced control of DOF).

But to be fair, assuming correct technique and 'good' copies of lenses and tight manufacturing tolerances (eg. no back or front focus), then both systems will produce great results. Lighting is perhaps more important with studio portraiture. Soft boxes, umbrellas, multiple flashes, background lights etc are all in order, depending on what effect you want to achieve.

For general runway photography I am guessing that it hardly matters which format you use. How large would you like to print? And then, what is the purpose for a print if you print real large? I don't believe very much resolution is needed for a billboard print that would be viewed from a far distance anyway...any of the standard 8-10MP cameras might actually suffice.

But hey, what do I know...I only print 8X12 prints, which stand up to scrutiny even at point blank range, and 8MP is enough for such a purpose for my case.