Don't worry about the chipset. 50/50 it breaks anyway. Buy the full replacement extended warranty.
I agree that you don't have to worry too much, because if you don't get Jasper you will get falcon. And even if there is an issue the warrenty makes it a moot point. But its not 50/50 at all. Its 50% of all 360s ever sold since launch. The first bunch (i.e pre falcon) was well above 50%. like 75% or whatever the hell it was. There were changes (to heatsink) pre falcon that lowered that down, and then with falcon it was largely fixed. Dropping it to like 10-15% or something (not sure the actual % on falcons) and then now with jasper its down to like 4-5% like it is with every electronic device you buy. The overall % is now down to 50% of all 360s sold. Its down to there because jasper doesn't barely fail at all like it shouldn't. There is little risk buying a 360 at this point.