If you scroll this board you will see I am mostly a fan of Kimpton Hotels, specifically the Monaco! If you are not familiar with the Kimpton brand of hotels, they are distinctive where other hotels are...just a place to sleep!
Of the choices you list, I would stay at the Monaco for it's vicinity in the middle of the historic district on lower King St., its access to the waterfront (3 blocks), bars and restaurants (too many to mention), and for its quirkiness and charm! I would call it a 'fun' hotel especially for us folks of certain age! They have a pool (indoor) and have interesting and fun activities for guests.
If you are comparing rates, you will see the Morrison House is quite expensive by comparison. It resembles a stately mansion, and were I looking to splurge, I might stay just so you could say you did....assuming you can swing a good rate compared to Monaco. It is about 5 blocks further west towards the King St. Metro, about in the center of King between the waterfront and Metro which is about one mile from shore to metro (Note: The city has a shuttle bus that runs the length of King from around 10am-10pm.) All the Kimptons have distinctive restaurants associated with them and Morrisons's is particularly renown.
I posted a link earlier this week (see below) discussing each of the 3 Kimptons.
The Hampton is the closest to the Metro on upper King (about 2 blocks) and is a great location if you want to get into and out of the city via metro. I have not been in the Hampton, nor had any acquaintance stay, so cannot discuss it's advantages accommodations wise.
The Holiday Inn First Street is north of Old Town and about 10 blocks away from King. I want to say they are the only hotel with an outdoor pool. The hotel is across the street from a grocery, and suffers from the dearth of restaurant choices. The closest Metro is Braddock Road and is several blocks walk across constructions zones and busy traffic.
If I am assuming you are here to sight see, my biggest suggestion is to avoid the rental car. Parking rates will destroy any advantage between the hotels, and outside of a trip to Mt. Verrnon, which might be on the average tourist itinerary, a car is essentially useless. I always recommend a cab ride to Mt. V if that is your intent! You will still save over daily rates and parking!
If you go Kimpton, sign up for the InTouch program in advance to take advantage of wireless services and other advantages the program provides.
I would go for the Monaco, for location and style, and their amazing customer service.
If you have other questions...feel free to ask. I hope you find this helpful.