Just some hypothetical answers on the F4:-
A1) A 3 platter drive will potentially be faster than a 4 platter drive and have better performance in sequential read/writes, however seek times may be slower. Please note that this is comparing drives of the same speed (5400 RPM for the F4EG) and TBH the actual difference in performance will be so close as to probably not be noticeable.
A2) The drive would theoretically (I seem to remember Samsung using the word 'statistically' when advertising previous drives) be more reliable but in practice this may not be so. AFAIK HDD manufacturers are very protective over failure rates, so actual statistics are hard to find.
A3) It should be quieter, but probably not so much as you'd notice.
A4) It should produce less heat but as the difference will probably only be a few degrees, I don't see how this matters.
A5) Cache size between 32mb and 64mb would make no noticeable difference.
A6) An un-asked question answered
. The F4EG should be more power efficient too, if left on 24/7 for 365 days compared to an F3EG you may save enough to buy a cheap can of beer
... or not
.
To sum up, if you're after a new storage drive because your old one is full then it makes sense to buy the F4EG instead of the F3EG, unless it's noticeably more expensive.
You could always wait for reviews though
.