Rain gear is a funny thing, what works for one is like standing under the shower for another. It is also an area where you generally get what you pay for. There are good suits by FirstGear, Tourmaster/Cortech, BMW, FroggToggs, and others. Some of the newest CanAm gear has been said to be good, and the Harley gear is top notch...if you like orange and black. Things to look for include ease of putting on in a hurry, wide zipper flaps that fold over double when closed, velcro sleeve closures (unless you have big wrists), stirrups on the pants legs to keep them down, velcro neck closures with tight necks, hoods to fit under your helmet, high necks (any thing that sticks out above it will wick water), breathable high-tech fabric, reflective piping or panels, bright colors for visibility, heat protectors on the legs, and double end cuffs for sleeve and leg. Two piece suits are easier to get in and out of, but can leak in a downpour. Don't buy too large, lest they flap in the wind and bunch up in front when you sit, creating a lake that will collect water and leak. One piece suits are dryer, but can be tough to get in and out of. Make sure you try them on to see that you can get into them with your boots on, in the rain.
I like the BMW coverall for a one-piece suit. My favorite two-piece is the Technics, but it may no longer be available. In the FirstGear and Tourmaster, the higher priced versions work best. FroggToggs don't work for me, but others like them. Get the motorcycle versions...they are more durable. I often wear two layers of rain gear...a good riding suit covered by a rainsuit. If you ride enough in the rain, you will get wet, but with luck, and careful selection of a suit, you can keep it to a minimum. JMHO