Staying upright is always going to be the best option, closely followed by fully comprehensive insurance & several witness's who will swear on oath that it really wasn't your fault.
We don't get to choose whether it's a big off or little off, or even when it will happen do we? All we get to choose is whether it's an almost certainty or just a rare momentary lapse of concentration.
Bars or mushrooms?
I remember the first time I spotted a set of mushrooms, in the paddock of club racing at Donnington in the early 80's & I remember thinking "yeah, they makes a lot of sense". They were skateboard wheels mounted on thin M5 bolts to the frame & you could see how they'd protect the engine during the almost inevitable slide down the track & go a long to making that bike fit for the 4th or 5th race of its day. Then they caught on, every clitoris in every pub carpark seemed to have several sets mounted all over the place for no apparent reason, even in places that no right thinking person could ever imagine hitting the ground in an off. They seemed to develop a presence on every aspiring riding God's plastic fantastic, much like rim tapes, reservoir socks & lever guards do today. They even developed their own logo's, carefully laser etched onto the sacrificial surface that grown men have been known to cry about should it ever be tarnished.
I also remember the first rider I ever met who sacrificed his ego & wrapped his engine in a cradle of Reynolds 531 steel tube that was undoubtably stronger than the rest of the bike put together. I don't like to namedrop but you will have seen him on your TV 'cos he's still the first choice 'stunt man' when it comes to 2wheels. I've seen this bloke get up & dust his leathers off while the bike is still cartwheeling @30ft in a ball of fire with bits coming off & even the director is looking for a safe place to hide.
You did ask " Engine bars or mushrooms? And why? "
What do you want? Crash protection or for anyone looking at your bike to think that you're cool?