How did I miss this question? Why didn’t I see it in my Q for you?
Let’s start with French Pinot Noir, the grape associated with Burgundy. If you’re buying in a store for $100 you should be able to get a Cote de Nuit (northern Burgundy) Grand Cru. Some village names to remember are Gevery Chambertin, Vougeot, Vosne-Romanee, and Nuit St. George. These are going to be richer (for Pinot) than the reds of Cote de Beaune (southern Burgundy). Village names to remember here include Pommard, Volnay, and Aloxe-Corton.
By “Cab” I’m assuming you mean Cabernet Sauvignon? Well now we’re talking about Bordeaux and specifically the Left Bank (as a rule left bank Bordeaux are Cabernet Sauvignon dominant and right bank Bordeaux are merlot dominant—the exception being Chateau Petrus which is located on the left bank and is always 100% Merlot—but $100 isn’t going to buy you any Petrus, anyway)
Just know that any just about Bordeaux you buy is going to be a blend of varietals including Cabernet Sauvignon, Merlot, Cabernet Franc, Malbec, Petit Verdot. (There are 14 Varietals permitted under AC regulations but these are the big 5)
Key districts here to remember include Medoc, Graves, Saint-Estephe, Pauillac, Saint-Julien, Margaux, and Pessac-Leognan.
Most importantly, and I can not stress this enough, find a wine retailer you trust.
Now comes the question of vintage. There are very few hard and fast rules about which years were better vintages but in general 1989, 1990, 2000, and 2005 can be counted on for both Burgundy and Bordeaux.
Happy Drinking.