Time to look at some facts rather than preferences ( nothing wrong with preferences but one persons choice may not be the next persons, its a subjective issue )
First , capabilities, limitations and power usage.........As for the last but one post commenting that the power usage may differ " Not by much", bear in mind the G3258 at TDP 53W is over double that of the 5350 at 25W.
Thats not a dig, its just a clarification...
As also pointed out in a post earlier it is not beyond reason to run the athlon passively, thus reducing power requirements even further. The G3258 will be much trickier to run passively. Power = heat = cooling need = power needed. It all adds up, both minimal power users anyway really but the big difference can be A/fan noise. B/The numbers on the annual electricity cost.
As for performance, the 2 CPUs are entirely different and although both are practically on a par for HTPC, in other areas the performances variations widen.
It all depends what you want to do with /on the PC. Also, bear in mind the AM1 platform was envisioned to go up against Baytrail technology, not mainstream PC.
Pros and Cons summary
Athlon 5350
Comes with more CPU cores,
Can handle more threads at once,
Supports AVX / F16C instructions,
Needs less power
Drawbacks:
Has lower base frequency,
Less memory bandwidth
Pentium G3258
Operates at much higher base frequency,
More memory bandwidth allows simple overclocking
Drawbacks:
Has fewer CPU cores,
Cannot execute as many threads at once,
Lacks some instructions,
Much higher power
Requires more cooling.
Longplay made a very good point about the 4000 display, the 5350 is capable of virtualization and the Pentium is not.
G3258 Athlon 5350
Intel HD Graphics GPU HD 8400
0.35 GHz GPU frequency 0.60 GHz
1.15 GHz GPU (Turbo)
3 Max. displays 2
AMD APU is one of its strong points, Intel Graphics can be excellent too, but the Pentium is restricted to the most basic iteration.
A discreet GPU is one obvious way to alter these performances, ( Although I cant think of a way of doing this without resorting to an MATX or bigger case and for me we are no longer talking about small form factor more like sub-mini tower territory ) Thats a preference.... I like true -ish SFF.
But..........Both manufacturers offerings of onboard CPU graphics is perfectly good and easily adequate for HTPC use.............
If I were to build just for HTPC it would be the Athlon 5150 or 5350. Lower cost and cooler/quieter.
Far easier to build a silent or near silent box with the AMD than the Pentium too, if it is an important consideration.
Anything requiring more number crunching is when the G3258 comes into its own.
I know most of this just echoes what you said Longplay but thought I would elaborate with comparison values.
Further, the FS1 socket is in line for its next generation of CPUs so then the single thread comparison may be closer, or even reversed....... FS1 platform is current and developing, the G3258 is an older platform ( Although still perfectly good for what we are looking at here )
Currently The Athlon 5150 and 5350 both also have DDR3L-1600 memory controllers, Intel is native 1333, anything else is overclock as far as Intel is concerned. Small point, but its one of the more subtle differences.
I have an mitx with each of the above CPUs and any one of them would be hard to differentiate from the others in HTPC use.