Hey picdev,
one very affordable way to have a modern IDE and do ARM cortex M debugging is:
- use (e.g. the community edition of) Visual Studio 2013 / 2015
- spend 70,- EUR on the non-commercial license of the VisualGDB plugin
I have done projects with ST stuff and got some impressions from the Kinetis branch of NXP.
(can't comment on the native NXP stuff (they did cortex M stuff before buying kinetis I think)
The Kinetis devboard + libraries I used seemed less of a hassle to get to work (more than just toglging a pin) than the ST stuff, and many people agree the ST libs are bad.
But the Kinetis libs were also not quite perfect, it's probably also not a high prio project at NXP / former Kinetis, similar to ST.
But... when using just CMSIS (register definitions etc) and the reference manual of an MCU, ST stuff works fine.
OR: if strictly non-commercial, and you'd like a library, perhaps
http://libopencm3.org/ could be a nice alternative .
I like ST's nucleo and discovery dev boards, debugger is already on those. Connect USB and you're done. (others are doing it this way too these days). I like the discovery more, while nucleo is geared towards arduino shield compatability, the discovery have the direct MCU pin names written besides the header pins instead stupid arduino pin names which I don't care about
If you did pic before, maybe start with a smaller MCU. E.g. the stm32f100 discovery, or stm32f0 discovery. The larger ones like F4 or L4 can be even more overwhelming.