I am heavily biased, but from those videos you seem to have more problems soldering with SAC305, where multiple touches of the iron of required.
Of course this is not conclusive that one is better or worse though.
I suppose this scant data can at least be used for generating hypotheses that would then need to be tested later (e.g. one wets better than the other), or to disprove really extreme hypotheses (e.g. "it's not possible to solder 01005 with SAC305.")
Temp here was cold board and 280C iron for SnPb verses 100C board and 350C iron for SAC305. So the leaded was on the cold side and lead-free on the hot side. The reason for the wildly different choices is that I'm just feeling around for what works best for me in terms of tools/alloys/temps and I am still early in that process (n00b.)
Try adding some fine pin pitch parts like TSSOP, etc.
I have done three more exercises now.
I soldered a QFP with ~0.6mm pitch using SAC305. That was a really pleasant experience from beginning to end with good results. Subjectively it felt similar to my experience of 63/37. (Sorry, no video of that one.)
I made a ham-fisted attempt to A/B compare 63/37 and SAC305 on separate quadrants of a significantly larger QFP. I made a total mess of both, partly due to choosing the wrong tips for such a large part, partly perhaps my soldering beginners' luck wearing off. I made a video that I haven't edited but could be scrubbed through:
https://youtu.be/j4WVN0HAKSoI then reworked that same messy chip with SAC305 and a better-suited tip. Just added LOTS of solder to dilute out the SnPb and tried to drag the solder blobs to the sides where I could suck them up. I did struggle with removing bridges and it's possible (hypothesis) that SAC305 was a contributing factor. Sorry, unedited video again:
https://youtu.be/jOhPbCtoYeYHere's one short highlight from the previous video of having fun playing with SAC305. It seems nice and playful in Amtech flux:
I'm not sure how far to pursue this now. My root problem is deciding whether to use SnPb or SAC305 for my own microsoldering that will be mostly assembling prototypes of e.g. PCIe cards. I have started with SnPb for fear that lead-free would be too frustrating and deter me from learning soldering at all. Currently though it seems like I could pick either one and successfully assemble my prototypes.
SAC305 is then attractive because I'd be able to sell my boards here in Europe (RoHS), I wouldn't have to worry about so much about contamination (using solder paste in a home office that my young kids can visit), and my techniques would transfer onto all the random electronics that I encounter e.g. laptops, phones, soldering stations, etc.
One further observation: I find that solder bridges stick out like a sore thumb with SAC305 because of the strong diffuse reflection. With SnPb I'm sometimes in doubt about whether I'm seeing a bridge or just wet flux in the shadow between pins because both produces mostly direct reflections. Sorry that I don't have a reference image for this at the moment, I know that would be more in keeping with the empirical theme here, so let's call that a hypothesis. This would be an advantage for SAC305 because I wouldn't even mind making a few extra mistakes if I were more confident that I would catch them earlier.