Heavy waterproofs are fine when you're struggling through a Cairngorm blizzard but they're more than you need for summer rain, even when it lasts all day. They can also take up a lot of room in your rucksack when not worn. Lightweight garments, weighing less than 700 grams, give adequate protection most of the time and won't weigh you down when carried. In fact some lightweight jackets are perfectly adequate for the most severe winter conditions.
The simpler design of lightweight models effectively helps keep the weight down. Additional features do nothing to make a jacket more waterproof or breathable and might compromise these properties, especially the second. How many pockets do you really need?
Two basic designs dominate lightweight waterproofs. The first is the traditional long jacket with two hem pockets, a map pocket under the front flap and a hood that doesn't roll into the collar, though hook and loop tags might be provided so it can be rolled away if required. This design works well for hill-walking and backpacking. A variation has the pockets on the chest rather than at the hem. I prefer this as it means the pockets aren't hidden under a rucksack hip belt.
The second design is intended for more dynamic pursuits such as scrambling, mountain biking and cross-country skiing where freedom of movement is important. These jackets are short, often barely below waist length, though many have an extended back. There are usually two chest pockets. As they are designed for high energy activities breathability is important so vents of different sorts are often provided.
More Than the Fabric
The performance of a jacket depends on more than the fabric it's made from. The overall fit should be snug but not so tight that you can't wear an extra warm layer under it when necessary. Sleeves shouldn't be so long they hinder use of your hands nor so short they expose your wrists. Cuffs should be wide enough to allow for ventilation but should also close neatly when protection is required. Length is a personal choice though it's worth noting that with short jackets you'll probably end up having to wear overtrousers more often.
Whatever design you choose, try it before you buy it and check the different features. Does the hood fit? Is there a map pocket? And is it big enough? It's best to find these things out in a shop not on the hill.
A good hood should protect against wind and rain and move with the head to allow for good sideways vision. Some do this but a surprising number don't. A hood that flops in your eyes and stays put when you turn your head so you find yourself staring at the inside might keep the rain out but will drive you nuts and could affect balance on steep terrain. A volume adjuster at the back can be useful for reducing the size of a hood. A stiffened peak protects against wind-driven rain and sleet but it must be stiff enough. A peak that flaps madly in the wind is worse than no peak at all. Hood drawcords should be easy to adjust - some can be operated with one hand - and shouldn't lash you in the face when it's windy.
Three types of hood are available. Fixed hoods that hang free all the time, rollaway versions that can be secured in place by hook and loop tabs and those that roll into the collar. Neither of the last two is needed for hill-walking but I wouldn't reject a jacket because it had one of them. However, compromises in hood design are sometimes made in order to get them to roll up neatly so do get the hood out and check it.
All the jackets tested are made from waterproof fabrics. Any design weaknesses that can let rain in are noted in the reviews. All the fabrics are also breathable, though how much body moisture they let out varies. The type of lining, if any, and the design affect breathability too. None of the jackets I tested stayed completely dry inside when I was working hard. In some cases there was a lot of condensation.
How long a jacket will stay waterproof and breathable depends on the quality of the fabric plus usage and care. Keeping a jacket clean is important as mud and dirt impede breathability. What you clean a jacket with matters too. Detergent is not a good idea as it can remove the water repellency. Instead use pure soap flakes or a special soap like Nikwax Loft Tech Wash or Grangers Extreme Cleaner.
For some reason there are far fewer lightweight than standard or heavyweight women's jackets and only one was provided for test though two small size jackets were also sent as women's jackets.