I generally prefer "silver" to silicon grease, but note that all the car peeps I deal with where heat coupling matters and you experience big boy temperatures have silicon grease packets, and certainly those thermal pads that might come as stock and rip if you so much as look at them and are thick enough to matter (they are however easy to apply in the factory and just about work so they get used). I certainly don't pay up for anything here beyond the £10/$15 syringe you might find in a half decent computer/electronics shop, and such things last me (theoreticaly a computer fixing type) years where I service several laptops and computers a year.
Beyond that if you are asking this question then the type does not really matter -- the differences between them at anything you are likely to be doing are negligible and offset considerably if you move from a hot attic to a cool basement/open a window/turn air conditioning on/crank the fan speed one more notch, or indeed blow out the dust and make sure air flow within the case.
Clean it properly and apply it properly (not too much, whether you spread it or allow the pressure to do it for you is even a debate) and you are good. None are going to last ridiculously longer than the other (timeline wise the device will probably need to be replaced/considered second rate long before then/need a general dedusting and cap replacement which means an extra 5 minutes to do paste is meaningless), be that much easier to apply (give or take the fondness for the almost liquid stuff that is going to be harder for no real gain and probably more expense because fashion) or give you particularly notable results. Some people however seem to enjoy getting lost in the weeds of such things, I treat them similar to how I treat those people that spend thousands on audio gear that makes bugger all difference that anybody outside a lab (and possibly not even then) will be able to measure.
If you fancy a minor science lesson. Properly flat things are hard to make (really hard, beyond what your $400 chip will cost) and as air pockets don't conduct as well as metal-metal contact then the super thin layer of paste is there to fill in said gaps and take it from a convection and radiation (which barely applies) model of heat transfer into a primarily conduction one in those local zones of air pockets. It is so thin that the thermal conductivity of the coupling medium in question, which either way is going to be reasonable, pales in comparison to its length (
https://www.toppr.com/guides/physics-formulas/thermal-conductivity-formula/ is a bit basic but serves as a reasonable intro). The people that sell it will have also checked it is not going to thermally decompose under expected temperatures (and given semiconductors fail to be semiconductors are comparatively low temperatures compared to things where heat transfer/heat engines is a concept you care about that means you will be under them) in any kind of notable timeline for these purposes.
