If the lens won't retract, that likely means that 1) your lens is out of alignment or b) your batteries aren't powerful enough, or 3) you have dirty battery contacts. The first can perhaps be handled by cycling your camera on/off several times and hopefully the lens will work it's way back into alignment. But don't force it if it doesn't. Move on to the next ... batteries. You may have gotten weaker batteries. Always use the batteries that are recommended by the manufacturer. But you want batteries with an "mAh" of at least 2500 to handle the high power needs of your camera. Dirty contacts can be cleaned with a pencil eraser. If these don't solve the issue, then it may need repair. Hopefully, it's still under warranty.

If it's batteries

Neither camera will do wonders in low light, but they're about equivalent. The Nikon, in this case, is probably the slightly better option due to it's faster lens and better LCD. It's a bit heavier though.