wow, those are opposite ends of the spectrum!
I'd say you need to take a really good realistic look at your family and personality before you decide for sure.
Greyhounds are big, mellow, easy going, laid back dogs... in general. They are usually quiet and soft tempered, even if they do like a good fast run once or twice a day. They are happy to share your home and your couch but they are not likely to spend all of their time focused on you and wanting you to play. They make great jogging partners, and will thrive on long walks/runs in the park. They make pretty good apartment dogs because despite their size they don;t actually need a lot of room (enough room on the couch to sleep is usually all they want).
Pap's are small, active, energetic dogs who tend to be more vocal and want a lot more direct interaction then a greyhound. They are also smart and you need to channel their energy into positive things. They are not a dog that lays around most the time, so you need to be the type of person who enjoys really interacting with your dog. I'm not so sure they would be that good for jogging/hiking. I know my small dogs would get sick of it fast and I'd end up having to carry them, lol.
Also keep in mind, many small dogs are pretty vocal especially when they are home alone and get bored. Living in an apartment that might be something you'd want to avoid so as to keep the peace with your neighbors... but that is an issue you could have with ANY dog.
In the end, a dog is an animal you really share every moment of your life at home with... as long as you have a realistic expectation of what life with a high energy small dog can be like if the little Pap has stolen your heart then go for it.
(I'm a big fan of greyhounds AND Papillions, Paps are on my short list of small dog breeds I would consider for myself, and greyhounds are on my short list of big dog breeds. So I can see why you are having a hard time deciding.)