Ef-s focal length

The only bad thing about crop is that there is a lack of wide angle primes within a reasonable budget.

An example of this is the 28 1.8. On crop body you would need a 17mm lens to be the equivalent of what the 28 1.8 is on FF and the 17-50 lens are a lot slower at 2.8 and don't have the same bokeh capabilitys of the 28 1.8 on FF as they are more or less F4.5 lenses since you have to multiply the aperture also on crop body.

F1.8 to F4.5 is a huge difference in terms of bokeh and low light capabilitys.

On FF you can get a nice trio of primes such as the 28 1.8, 50 1.8(for backup or the 50 1.4) and the 85 1.8 and possibly a long telephoto like the 135F2 or 200 2.8.

On crop this is not possible and it becomes very expensive to get wide angle lens and the crop body wide angle lenses are mediocre at best as they are slow variable aperture lenses that cost $600+ with plastic bodys such as the Canon 10-22.

If you need wide end and speed along with bokeh go FF.