I'm not the OP, but when I had the 6+ I had issues keeping my music or podcast app running with 2-3 tabs in safari; they were tech sites and content heavy. It wasn't the stock music app so I guess iOS gave it lower priority than safari tabs??? I would open it, while it was playing music, and the app would reload causing the music to stop. It might not be RAM per se, but I haven't had that issue on my 6s nor on my Air 2. I don't have the 6+ anymore, but there are really only a few key differences between it and the two devices I use now that have none of the issues. The 6s runs an A9 processor with 2GB of RAM on ios9, while the Air 2 is a tablet running an A8X with 2GB of RAM. There's really no fair way for me to test it as I don't have the 6+ anymore and there are those key differences listed above that could have contributed to the different behavior I've noticed. I went with the common piece between them (RAM) for an easy conclusion as to what made my problem disappear. Not scientific or through, but good enough for me.
precisely. Perceived lag is typically not attributable to CPU speed so much as it is to lack of free memory/RAM.
That being the case, I think the 'best bang for my buck' going forward is to hold off until there's a RAM bump at the 4.7 form factor.