I own a Nikon D5300 body, but wish to upgrade to a Pro FX body in future (not any time soon).
The reasons I'd like to choose the former are:
The reasons I hesitate before making the purchase are:
Can anybody please clarify my doubts? Apart from the points I have highlighted, is there any other major/minor concern which I have failed to take care of?
"...all Pro FX bodies have AF motor built inside the body. Hence, SWM in 'AF-S' lens is redundant."
Not necessarily. The performance of camera based focus motors and lens based focus motors is far from identical. SWM lenses tend to focus faster and more quietly than their non-SWM counterparts. Add the mechanical interface between the body and lens and the noise gets even louder. Newer SWM lenses when used with newer Nikon bodies also tend to focus more accurately as the lens confirms more positively to the camera the exact amount of focus element movement actually effected via use of a focus position sensor.
Regarding optical performance (hint: there's a difference), please see Do Nikon AF-S lenses perform better than AF lenses?
I think you forgot one really basic thing. Image quality. You may want a side-by-side comparison of the much older D design to the digital-era G design on a full-frame camera, such as this one on the-digital-picture.com, where the two lenses are tested on a D3x. In that comparison, mousing over the test chart crops will switch between the two test setups. If you plan on using the lens wide open at f/1.8, there's kind of no contest.
The biggest thing to understand isn't just the features and reputations. But the fact that the 50/1.8G design came out in 2011. The 50/1.8D design dates from 2002, but its optics are unchanged from the non-D 50/1.8, which came out in 1986. They learned a lot about improving lens designs in the intervening 25 years, and digital shooters are far more critical than film shooters were. Hence the glass update.