DX 55-200/300 or FX 70-300

hoping you guys and gals may be able to assist, my Sigma APO 70-300 lens has started to suffer and getting sharp images from it in anything but bright light or the moon is getting frustrating, and the other night i caught it in the act of slipping affecting the focus.

It seems ok in day light on autofocus but its the manual focus it suffers specially above 135mm.

im using it on a D5200.

So im now looking for a new lens.

im looking at the DX 55-300mm or the FX 70-300mm , most of the reviews suggest that the 70-300 is faster on auto focus but the image quality on both is very similar, if this is the case id rather take image over focus speed, i know its needed for birds and sports, but i rarely photograph sports and i wait for birds to land giving the lens time to focus.

other than the obvious cropped and full frame differences is there something im missing stopping me purchasing the DX 55-300?

thanks

I would suggest the FX lens. If you never go to FX then no big deal. However, if you do go to FX and bought the DX lens then you are losing part of your field of vision that a DX lens simply can't put on the sensor.

I have the 55-300 DX. It's a good lens. Not a great lens but a good one.
It's worth having around for one reason, price. Refurb 55-300 DX lenses are everywhere for $200.
At that price it's a steal. At it's normal price it's meh.

I paid $199 for my refurb. As long as you work within it's limitations it's a good lens.
It's great for everything but sports or a moving image.

I also have the 55-300 for a walkabout lens during the week, if I knew now what I knew when I bought it I would have gotten the 70-300.

Get the 70-300 it is a great lens and if you move to to FX some time in the future you have the lens already.