I would definitely look to an ARM platform, for low cost and wide support. Rightly or not, ARM are basically taking over the whole market. Even Freescale have dropped development on their whole DSC range, replaced with ARM Cortex based Kinetis range, which are fairly standard Cortex offerings. The Kinetis KV are "specialised" for motor and power control applications, but they are pretty standard apart from some Freeescale IP blocks borrowed from DSC.
Freescale are putting a lot into Kinetis, they have skipped M3 in favor of M4, and as a result have some very low priced M4 MCUs. They also provide free software with Kinetis Design Studio for most of their Kinetis chips. They also have cheap dev boards with the "Freedom" badge, and high-end "Tower" kit.
Freescale's documentation and support let them down, and their chips lack easy to use bootloaders. Not really a problem for professionals, but for hobbyists and tinkerers a JTAG adapter is essential.
STM and NXP both have plenty of easy to use and capable Cortex chips, and the built in bootloaders make these much easier to get going.