The general rule is if the wine is not good enough to drink, its not good enough to cook with. I have seen poached pears made with everything from dessert wines to big dry wines and everything in between. Its all a matter of preference. I find the "lighter" varietals tend to cooperate better with the spices and flavors of the dish. But, again, that's my preference. Some like the flavors produced when dry wines are met with the spices and sugars.
Knowing the details of your recipe would allow for more specific suggestions in terms of wine.