WR3000: Should be avoided at this point unless you can get it for cheap to work as a dumb AP.
WR3000S or WR3000E: If you only need 1Gbps ports and 256 RAM.
WR3000P: (only supported in snapshot) Has 1x 2.5Gbps and 4x 1Gbps ports, same as WR3000H but 512 MB RAM instead of 256 MB and an USB2 port.
Can’t really comment on price and availability as I can only find the original WR3000 for sale in my country.