As with the 8 bit and 16 bit pics, with Microchip you know that the PIC32 or something better will still be there with the same pin-out in 10 years time. This is probably more important to me than having the latest and greatest core or an extra MB of flash as it means that if I need to support or upgrade my customer project for however long I can generally pop in a compatible chip that compiles the same source.
Microchip make a few mistakes like everyone, but they are pretty good at owning up to and eventually fixing them, they keep there prices competitive, and in 1 off quantities, support DIP parts, generally have the popular stuff for delivery from stock next day, and the IDE while not perfect is still amongst the best and supports the whole product range for free. The optimisations that are turned off in the free version generally affect the code size not performance and then not by much, above all it still compiles and flashes a 32K pic32 C program in under 7 seconds on my Core i5 laptop (984 lines, just timed it!)
This is not to say the choice of ARM is not a good one, ARM chips are generally slightly cheaper and have better performance, RAM and Flash options, but the amount of one-upmanship going on in the ARM market and different chips out there every other day is quite staggering to the point of confusion, also I'm not sure if there really is room for half a dozen ARM chip manufacturers, and with my luck I would pick the wrong one!
if your on this roller-coaster, then stick with it and enjoy the ride, but I prefer a more sedate ride and in times like this I am really glad I work for myself and don't have some trendy manager choosing which chip I use.