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Both will work equally reliably, it all depends on the skills of the designer not the chip.

 

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Microchip has extremely low power consumption in sleep with their "nanoWatt" line.

It comes down to coding in either case. Most issues will likely be software bugs instead of hardware issues, assuming the hardware (PCB, other components, enclosure) is done properly. This is a huge area of its own to cover, but a stress test, trying unexpected inputs, and trying all the incorrect connections one could make in the future to be sure it doesn't go into meltdown both physically and code-wise.

Is there a reason to use the PIC24 line over the PIC18 line? The PIC18s are pretty powerful, and typically use less power in sleep. For battery operation, try to get the code small so the uC (whatever you choose) can be run at the lowest clock speed possible, running or sleeping. The "Dynamic Clocking" options should be available in all uC choices, and something you should look into as well.

 

That didn't work out so well for Dell.

Huh? I'm missing something?

 

Dell has a lot of hardware failures . But I've seen some of them software failures
too. But whats dell got to do with a pic ?

 

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Dell put out one of their business machines and put in 100000's of bad cap's that were supposed to be up to spec but weren't. So they all blew 2-2.5 years later. Some business's and schools had 60% failure rates in a 3 month period because of it. They literally had 600 computers die out of 1000 in a 3 month period.

That was the first batch of counterfeit caps that showed up, luckily, they failed while most were in warranty. There are still tons of counterfeit caps out there, and they still fail quite often, but the media doesn't make a big deal out of it since they cannot pin it on a single source like they could with Dell.

 

I haven't had any experience with the NXP series of μC's, but I have with PICs. The PIC series of μC's, as you probably well know, are great for low-power applications. I'm sure that they both can easily provide for the operations you will need in your design, so power consumption would probably be the main issue for you. I am dubious, though, about whether there is much of a difference anyway in that regard. So as blueroomelectronics mentioned, it's really up to you through the cognizance of firmware.

 

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If performance is your criteria and price per uC isn't an issue then any ARM controller with ARM9 will be great. By that I mean the price of the whole CPU subsystem that includes flash and RAM. Integrated devices will be much better here, since it doesn't seem that you need too much of memory.

Even Atmel has some great AT91SAM9xxx controllers, NXP has some new controllers coming out LPC17xx and 18xx with ARM Cortex core which should be much better off.

On the other hand, PIC24 controllers are very low power devices but the performance is about 1/6th to 1/4th of a ARM7TDMi controller and even lesser compared to ARM9 (which can go upto 200MHz).

Both devices have their errata sheets, but are equally reliable. So after reliability, battery and power, your criteria could be performance.

 

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