cheapness of (assembler) code development
SILabs comes with a FULL UNRESTRICTED Keil

(sorry folks, can't/won't do C).
that limits you severely, since all reference code these days is in C

I'm sort of frightened by Silab's wide range of devkits. If I decide the target processor I initially select is wrong, do I have to spring for a new DK?
yes, but select one that is way beyond what you think you need and you will be 'safe'

I note some processors use JTAG and others C2. Any major differences, or are they just different interfaces? same dongle