Jumping in here, I think there have been some excellent points.
Hotel preference is subjective to what you're comfortable with... both price and comfort-level. I will say, if you're staying on property, the resorts are all unique, but none are actually bad. I don't like the Grand Floridian, but I love Old Key West. It's just personal style and preference.
If you want to do both the parties and the parks, think long and hard about the distance between the two. The host hotel may not look that far away on a map, but that is NOT a fun drive with traffic and definitely would get expensive Uber/Lyft-ing back and forth. From host hotel to the MK train station, I'd say you'd need at least an hour, but it would probably be closer to 1.5 by the time you drive, park, walk, tram, security, monorail/ferry. If you're only doing that one day, though, it's certainly less expensive to stay over near the parties and you wouldn't have to drive to those. And, if you're going to P-House or something downtown, I haven't cabbed it in a while, but it was close to $50 each way the last time I did from Disney (which was probably 8 years ago).
My opinion is, it's hard to do both, but it sure is easy to have fun no matter what you decide to do or stay!