Which is better is a function of the quantity, intensity, and duration of the rain you are expecting to encounter in the area in which you are hiking.
I've used the RainShield suit off and on for years where the rain is light or of short duration (like the Sierra where afternoon storms are usually short though intense.) The jacket also works well as a windshirt and around camp as a light insulating layer. Durability is an issue, and packstraps will cut through the shoulders in a few hours. Pant seams are especially vulnerable; go up at least one size. These days, I prefer my Gatewood Cape as it also serves as my shelter. If I want to hedge my bet, I can always toss in just the RainShield jacket.
For areas like the North Cascades, where a cold, steady rain can last for days, I carry a full-on rain suit - Golite Reed pants and Montbell Peak jacket. I used to carry a full 3 layer Gortex suit up there but switched to this setup many years ago to save weight and bulk.
No matter what you choose, be willing to bail immediately if it turns out you made the wrong choice. I was run out of the North Cascades at Harts Pass one year by a storm that had even the local hunters bailing. I was wrapped up in my Gortex suit over a 200 weight windblock fleece jacket and long underwear, pile hat and gloves with Gortex overmitts, hiking uphill (but not sweating), and could not stay warm. Horizontal, wind-driven rain that lasted ultimately for 5 days without let-up. Walking and sleeping in clouds of wet fog with constant rain. A RainShield or FrogTogs suit would have been a disaster under those conditions.