It is true that some "trial versions" do NOT support all video formats or some HD features. However, one would think that MOV and MPEG would be in the most common category.
Before you buy, first confirm whether you have the correct system requirements. What are your PC specs? What kind of MOV or MPEG are you trying to edit? How have you edited them previously? Might the MOV be a high bitrate h.264 HD version your PC does not support. Might the MPEG be 1440x1080i or 640x480? Or might it be an MPEG-4 or MP4 variant?
Great to hear that someone is prepared to cross test various NLE products. S14 should be able to support many types of MOV or MPEG, since Studio 12.1 did, provided you have the right PC.
For the record, Studio 12.1 handled some, but not all, brands of MOV h.264. HDV MPEG2 was no problem. Certain types of MPEG-4 or MP4 shot with micro devices sometimes presented problems. Sometimes the video format types were themselves unsuitable to any good image quality on a big screen. Other times, the shortcoming was with the software. Whether Studio 14 addresses most or all is worth a test. Forum participants do not, unfortunately, have all the relevant file types. And sometimes a clip may preview well in isolation, but still not digest effects or transitions properly in the context of a large project. In some instances, dissynchronized sound is obvious immediately; in other cases it creeps up over the duration of a long clip or timeline.