Progressive Lens vs Bifocal - Which is Better for You?
Pretty good rundown, to which I will add the following regarding progressives:
To minimize the distortion around the central intermediate zone, choose frames with small lenses that position the lenses as close to your eyes as possible. The closer they are, the larger the clear center zone will appear.
Don't cheap out on the material and get the latest computer-controlled ground lenses, particularly if it's your first pair of progressives. If your optician offers an "interview" to personalize the position of the distance/near zones, use it. It seems like a gimmick but it really does help personalize the progressives to your activities.
Progressives are difficult to get used to and it doesn't take much to make them unsuitable and difficult to live with. So stack the odds in your favor to make them work for you, even if it's more costly. If you can't get used to them, the entire cost of your new pair of glassess will be money down the drain and you don't want that.
Give progressives a chance for at least 4 weeks, even if they seem to give you splitting headaches or nausea at first. Again, they're not easy to get used to. Once you are used to them though, they're a life-changer.
I strongly disagree on the small lenses. Now your reading zone is a larger percentage of the lense, so you have to move your head more. A larger lense enables a lower rate of change from the central reading zone to the distance zone.
How the zones are designed is a significant factor too. You can have a larger reading zone (say you do close work most of the time), or a smaller reading zone if you only occasionally do close work. It's really important to work with an optician to get the right setup, especially for your first pair.