If it's low RAM and single threaded then I would expect every tier to perform identically.

(Also I was just looking at the pricing, you don't get any extra CPU cores until the $84 tier!)

Thanks for pointing that out. I had thought maybe as the tiers went up you'd get faster CPUs, but upon reflection the pricing schedule seems to confirm your point. I guess they are completely virtualized because there is not mention of CPU type on the pricing page.