I've just purchased and 8gb stick of DDR4 RAM (Later on I'll uograde to 16gb) along with a 240gb SSD.
If your motherboard has 4 slots then you're better off with 4 x 4gb.
2 x 4gb is also better than 1 x 8gb.
Unless you only have 2 slots and plan on running 2 x 8gb eventually.
in your opinion would you rather have say 8 or 16 gb of ddr4 rather than 32 of ddr3?
Other than ddr4 having higher clock speeds there's not a massive difference. It's arguable whether the typical end user would notice any difference at all.
But... that's irrelevant as they're not 'backwards compatible' You can't use ddr3 in a ddr4 motherboard or ddr4 in a ddr3 motherboard. So any comparisons would also involve different motherboards and processors.