Probably a bit late in the day but a lot of searches on this topic lead here.
I don't agree with anything I've read here.
If you have 60p or 60i or 59.94 fps or 59.94i or 50i or 50p or 30p there is only really a couple of ways to convert to 24fps successfully and create a reasonable approximation of film look.
With interlaced footage you deinterlace it to turn it into progressive frames , with 60i for example you can do it a number of ways and end up with either 30p or 60p depending on the deinterlace type. You then feed the progressive footage through a vector based (oprtical flow) based retimer and it will reinterpolate the entire sequence to your desired timebase.
Some will also allow you to add intraframe motionblur , for example a 60fps sequence is going to be exposed for 60/shutter speed . What you need to approximate a film look is 1/48th exposure time per frame, you need to add enough motionblur to compensate. For example if you shot at 120th sec at 60fps you would need to add the equivalent motionblur per frame of 1/48th exposure time to the interpolated 24fps.
To be honest 120th would give so little motionblur at 60fps that you may as well specify a full 180 degree shutter angle type motionblur for 24fps interpolation.
Packages which will allow this are Kronos/Furnace ( Foundry) and Twixtor and the Oflow tools that come in Nuke.
The process will leave artifacts , how noticable they are depends on how well you tune the interpolation , the activity in the footage and how well you do any resulting cleanup of the artifacts.
And the comment on VFX preferring higher speed is only relevant for a few given situatons such as technical plate shoots . Do not prioritise your shooting speed just for VFX , they can cope with everything just fine.