Pruners come in two basic styles: anvil and bypass. With anvil pruners you have only one sharp cutting blade, which closes against a dull bed (the anvil) to sever whatever. Bypass types are more like scissors, with two sharp blades, one of which secures the branch while the other moves past it, cutting as it goes.
Anvil pruners cannot be brought as close to the cut as bypass types, but they do have two advantages: only one sharp blade means only one blade to sharpen, and the mechanism does give a bit more leverage. Though this can make a difference if you want to use a small pruner for very thick or very hard wood, it’s usually easier to use a bigger pruner for heavier jobs and stick with bypass for everyday use.
Bypass pruners come with all kids of blade lengths and angles, with and without ergonomic handles, and in special versions for lefties. They also come in a wide price range, with the best-made costing two or three times as much as the cheapos. Fortunately, even the most expensive pruners cost less than dinner and a movie for two, so there is no reason to stint. Just remember the old saying: good tools make all tasks go lightly.
In fact, it’s best to have at least two pruners, one saved for rough work (at ground level, for example, where you might hit gravel) and one used for delicate operations like removing spent lilac blossoms.
This will let you go a bit longer between sharpening sessions. But those sessions are as important as the pruners themselves because it is absolutely essential to make clean cuts when you are pruning shrubs. Wood that has been torn or crushed, as is guaranteed to happen if the pruners are not sharp, is (literally) an open invitation to disease.
Just as it’s better to plant a five-dollar tree in a ten-dollar hole than the other way around, it’s better to have a pair of sharp cheap pruners than to work with quality tools that have been allowed to get dull. If you don’t want to sharpen them yourself, be sure to have them sharpened regularly by a professional — your local nursery or garden center can usually recommend someone. Keep your tools clean and oiled between uses so they don’t rust, and they should serve you well for years.