The software serial on the Picaxe will run at 19k2 on any pin but not particularly reliable I think. It also has a hardware serial port which is independent of the download circuit which is usefull. The hardware serial will write directly to the scratch pad but 1024 bytes is much better than 127. As you say the C style language appears a much lower level language than BASIC so must be more powerfull. Of particular interest is updating firmware without needing the program editor.
Strange that the Arduino is only really designed for one true serial port.