So far, the Atmel Acquisition by Microchip is going pretty well, I think. I haven't seen any major complaints (here, or on any of the more technical AVR-related discussions) that can be blamed on the merge.
Microchip PICs are somewhat older than Atmel AVRs, and it was obvious when the AVR was first released that Atmel was targeting PIC users. It was a hotly waged war for quite a while.
There are actually three different lines of PIC microcontrollers:
1) 8bit PICs like the PIC16x and PIC18x chips. These are generally rather old-seeming chips, and are sort-of ugly and unpleasant to program. They don't support the C or C++ language very well.
2) 16 bit PICs like the PIC24x and PIC30x. These are supposed to be better.
3) 32 bit PIC32x chips. These use an "industry standard" MIPS architecture that is comparable to the 32ARM chips used on Arduino Zero and Arduino Due. They (some of them) are supported by the MPIDE Arduino core that you can get here:
https://github.com/chipKIT32/chipKIT-core One of the interesting features is that there are some PIC32 chips with 256k of flash and 64k of RAM in DIP packages!