I like flye motions for the pecs on my shoulder press days but all flye motions are not equal.  So here's some of the drawbacks and benefits to each one (and yes I still use all three)

benefits - 

the most basic so every gym will afford someone the ability to do these.since every gym has dumbbells and a bench

Allows for individual mechanics since you can dictate the arm path accordingly 

High level of progressive overload 

drawbacks -

Limited resistance profile - Always heaviest at the bottom, so if that torque bothers someone's shoulders (it does mine at times) then it's a no go

Because it's always heaviest at the bottom this is where both the biceps and pecs tendon are lengthened so if there's any micro injuries at the MTJ level that could lead to pec tears/biceps tears

benefits - 

most gyms have one

Usually stacked heavy enough for PO (if not everyone has a gympin now)

drawbacks - 

Many of them have a fixed motion so if that doesn't agree with your structure it's going to feel like ass

Outside of Prime, all have a fixed resistance profile so if that too doesn't feel good for your shoulders or elbows then it'll be out

benefits - 

will work with whatever your structure is

can be setup to offer up different torque curves (resistance profiles)

can be used for different regions of the pecs with just a cable height change 

drawbacks -

some gyms don't have a proper station for cable flyes

some stacks aren't heavy enough for strong guys (again a gympin could be used)

have to drag a bench across the gym usually for best stability 

All of these ARE FINE TO USE.  And there's def benefits and drawbacks to all (as you can see).

But from an actual exercise biomechanics and utility standpoint the cable flye is probably the only s-tier because of ability to fit every single person's structure, offer up different resistance profiles, and easily train each division of the pecs with ease

- Paul Carter Hypertrophy Coach & Author