Pavilion 14-N059TX, i5-4200U + Nvidia GT740M@RM2099[2.03kg], 4GB, 750GB, W8

14R has quite a range of specs, I supposed you mean this:
Inspiron 14R, i5-4200U + Nvidia GT740M@RM1849 [2.32kg], 4GB, 500GB(5400rpm), Linux, 6 cell; W8@RM2049

Spec wise, other than the HDD capacity, no major difference.
Other things such as keyboard, touchpad, screen, speakers, aesthetic, etc, are subjective, you have to make the call yourself

Looking at your usage, both are actually packing too much power (well, since you did not mention what "task" you multi )

Both has 2 RAM slots. If you multi-task a lot, buy more RAM (4G stick ~ RM100, 8G stick ~ RM200).
Yes, for both models, you could buy SSD to replace the HDD.