There is no perfect grip for volleys in tennis. The Eastern forehand and Eastern backhand grips are strongest physically, but you have to switch between them, which requires extra mental effort and time. The Continental grip saves you from having to switch, but it's weaker physically and can feel quite awkward to some players on the forehand side.
If you can get comfortable with the Continental grip, it's your best choice. Remembering to switch grips can be difficult in certain situations, and in extremely quick volley exchanges, such as when all four players are at the net in doubles, the time it takes to switch grips can be an issue. If you play serve-and-volley, as most advanced doubles players still do (even while serve-and-volley becomes rarer in singles) it's handy to keep the Continental grip you're using for the serve as you come forward to volley. The Continental grip puts the racquet face in a naturally open position that's well suited for applying backspin to low volleys, although the Eastern grips are also comfortable for low balls. Most pros use the Continental grip, as they have plenty of strength to overcome its physical weakness and plenty of practice to get used to it.
The Continental grip doesn't suit everyone, though, even at the advanced level. On the forehand side, it can feel extremely awkward, especially on balls more than a foot or two above the net. Many tennis players are taught that they must use the Continental grip, and they try, but if you observe closely, you'll often see them hitting volleys on both sides with a grip closer to the Eastern forehand. This relieves the awkwardness of the Continental forehand volley, but it's so weak physically on the backhand side that a hard shot can literally knock the racquet out of the hand. It may seem strange that players would use a grip with such a major flaw, but despite the almost-Eastern-forehand grip's weakness on backhand volleys, it doesn't feel nearly as awkward to many players on the backhand volley as the Continental feels on the forehand volley, and the body tends to overrule the mind on this sort of question. In this case, the body fools the mind, as most players who use the almost-Eastern-forehand grip have no idea that they're not actually Continental; they just think they have an unavoidably weak backhand volley, and many of them end up, as a result, using a two-handed backhand volley, which has a ton of flaws of its own.
A two-handed backhand volley can work well if the ball comes to the right spot in relation to your body, but it breaks down quickly if the ball is too close, too far, too low, or too high. You can try a simple experiment right in your living room, without a ball, to see one of the two-handed volley's limitations. Pretend someone has hit a hard shot right at your belly, and try to block that shot with your strings while holding the racquet with two hands; it's nearly impossible without an extreme contortion you'd never have time to execute. Try blocking your belly with your forehand; same problem. A smart opponent who sees you using a two-handed volley will make your belly a prime target--or, if that opponent is of the gentler type, will just hit to one of your other two-handed weaknesses: low, high, or farther away from you.
Many players get to a two-handed volley not by giving up on a weak one-handed backhand volley grip, but because they just bring their groundstroke grips up to the net. Now that forehand grips have become more western, with the Semi-Western the current average among pros and advanced juniors, bringing groundstroke grips to the net tends to cause weak volleys on both sides, as, except for swinging topspin volleys, the Semi-Western grip only works decently on some high volleys, and the full Western is extremely awkward at any height. Hitting nothing but swinging topspin volleys isn't a solution either, as they only work on slower, higher balls where you have time to set up a big swing.
If you can get comfortable with a Continental grip, you'll be all set for volley grips. If Continental just doesn't suit you, learn to switch between the Eastern forehand and Eastern backhand grips or, as some players prefer, between the Eastern forehand for forehand volleys and the Continental for backhand volleys. You may have trouble switching in time in the quickest doubles exchanges when everyone is at the net, but you'll lose many fewer points in those fairly rare situations than you would if, in trying to avoid switching, you settled on grip that's almost an Eastern forehand and thus extremely weak on the backhand.