Had a Marlin 39A a while back. Never did a serious accuracy test on it, but I remember hitting a 50 meter 8 inch gong pretty much 99% of the time, with stock iron sights, standing off hand. I know that doesn't say much about rifle or the shooter.
For some reason, it would drop a cartridge (to the ground) if I cycled the lever with the ejection port facing down. Not really very smart gun handling, but because of that, I traded it away. If cycled gun upright, it never failed to eject, or failed to feed.
At the time, I had an Anschutz 1416 double set trigger and it was definitely more accurate. I always loved bolt-actions because of that 1416, so to this day, all I have left are bolties after selling off all my semis.
If you are after accuracy, I would say bolties are typically more accurate, unless you have an ultra special Marlin 39 or Henry. Only reason I'd go lever is for the fun factor.