My initial thought is that if you are concerned about an imminent failure, you should not have purchased either of the two vehicles. It is true that the Classic has a number of trouble areas, like the traction battery, electric steering gear, and transaxle. It is also true that the 2005 with 151K miles is at or near "end of life" and it is certainly not impossible that the traction battery might fail, or for that matter the inverter or transaxle. So it would not be surprising that either car might have a major problem tomorrow, or in the next year, or who knows. However since you already own both, if you don't need both cars, then I suggest you determine which car can be sold at the least financial loss to you, then bank the proceeds in the event you need to repair the remaining vehicle.
Inverter and transaxle failure is much more prevalent in 01-03 than it is in 04-09. Sell the '02. It is probably more marketable, given the condition and "little old lady from Sweet Home" provenance. You could put 10 years, 200,000 miles on the '05 and not have any problems. But change its transaxle fluid NOW.
