You won't get an increase in ROF by changing hopper, however with a force fed hopper you can be confident a ball will be ready
If you are able to shoot as many balls as you pull the trigger for then your hopper is meeting your ROF
With the gully you don't really have a basic gravity feed, you have a next generation gravity feed
Excluding unusual things such as spring feeds and the qloader the basic hierarchy of hoppers is:
True basic gravity - balls drop at a maximum of the speed of gravity, but can be jammed if two or three balls meet at the top of the neck, if the paint is sweaty / greasy this may aid jams, but as long as you are moving or the gun has a bit of a kick then the one or two balls ahead will be ready and you will dislodge the jam in time. These hoppers gave the term 'shake and bake' to ensure that balls are separated
If you have a gun with eyes to ensure a ball is ready then it will just refuse to shoot until a ball is in the breach, this prevents chopping because a ball is still dropping when you fire
Next in the pecking order (but not in timeline) is the anti jam gravity hopper (eg proto primo) the shelf or gully adds another stage making a longer channel of balls ready to feed. So jams should not cause a break. These are a good buy and have value for the player who is not shooting ropes, and don't have batteries to fail
The next generation, which is the electric agitated hopper, still relies on gravity to feed but had some form of agitation. Probably with a switch or sensor in its feedneck that identifies a gap in paint (and thus a jam or an empty hopper) and starts the electric motor to shuffle the balls and release a jam
This still does not promote any bps, but if the battery runs out at least it reverts to being a gravity hopper
The final stage is the force fed hopper. These run on batteries with the exception of the qloader which is spring loaded at the pod, and a force feed with a flat battery - which may have a manual option.
A force fed hopper with a flat battery is useless, all you can do is manually wind the balls in if you have that option
But the benefit of a force feed is to increase the guarantee of a ball being ready, it is literally forced down into the breach, so as the bolt goes back the next ball is pushed into place and you know it is ready unless your bolt is cycling faster then the hopper can feed
If you don't get chops, or miss fed balls then you don't need to upgrade. But going to a force feed now without needing to go top of the range can give you peace of mind and future proofing for your next gun