How should I connect batteries in parallel?
The resistor solution has the main disadvantage that there can flow a (rather large) current from one battery to the other. This may reduce the life of the battery receiving the current (you're not properly "charging" it).
I would go for the diodes. If one battery's voltage is higher than the other this battery will be the only one supplying current, until both voltages are the same. From that moment both batteries will supply current.