I really, really to do not want to feed the troll-like responses to anything that may be perceived as snobbery or anti-Club Carlson. This thread has already taken on a much nastier/defensive tone than is necessary. If you spend a lot of nights in hotels, you'll notice a difference after a while. I've spent almost 1/2 of my nights over the last 25 years in hotel rooms of all price/quality ranges.

If you're happier with a Radisson in Paris than the PH Vendome, that's great. That's not meant as an insult; as long as you're happy with the Radisson, why spend the extra money? I've stayed 2 nights in a suite at the PH Vendome, courtesy of my free Hyatt Visa credit card nights. It is one of the top hotels in the world; I had a great stay there. If not for the free credit card nights, I would have stayed somewhere less upscale. Probably the Westin Paris Vendome - same location but much less expensive. That's still more expensive than any Radisson in Paris so I'm sure I'll get flamed for that choice. However, I'm an SPG Plat and Hyatt Diamond so there are other perks that come with top tier status with those hotel chains.

I've seen a post here where someone said that they'd never pay more than $200/night for a hotel room. I understand that; I used to have the same opinion. I'm in a different point in my life where I can afford to spend a bit more on hotel rooms than I used to. Last summer, we traveled to China and we stayed at the St Regis in Lhasa Tibet. This is a place where you can get a decent hotel room for $50 or so. Since it was my daughter's birthday while we were there, I used cash and points for the St Regis - 10K pts + $180 per night. Fantastic hotel, but I'm sure many would call it an overpriced piece of crap. To each his/her own.



Trying to drag this back to topic:
Sosamo, if you're going to Paris, you will likely visit Versailles. A few things:
1) The Palace is closed on closed on Mondays.
2) I highly recommend that you spend one night in the town of Versailles (it's quiet) so that you can arrive at the Palace early in the morning. The lines get extremely long for entry. Just don't make it Sunday night.
3) Buy your Versailles tickets at the hotel concierge desk the night before - this will save you time at the Palace.
4) I'd recommend the Waldorf Astoria Trianon Palace Versailles. It's the nicest hotel there, but likely to be cheaper than any nicer Paris hotel.
For Paris:
Buy your Louvre tickets from your hotel concierge desk. This will save you a lot of time in line. There's a special entrance on the side of the Louvre for those tickets - it takes a while to find it, but it's a huge time saver.

For London:
The Tower of London is a must see, but it is off located by itself. I recommend you stay at the Andaz Liverpool street. Stay there on a weekend night; the hotel is used by businessmen/bankers so the rates are HIGH during the week and LOW during the weekends. The hotel is right next to the Liverpool Street tube station and is walking distance from the Tower of London (only a few blocks away). Or you can choose another hotel that you might think is a better fit, but I recommend booking it for one weekend night due to the much higher prices during the week.
If you guys are into rock and roll, I recommend a rock and roll tour. They're a lot of fun.

Since you'll be gone for 19 days, you're going to need to do laundry. I usually plan one or two days to get laundry dropped off at a local Laundromat/cleaner. That's going to be a cheaper option than having the hotel take care of your clothes. Hunt around on Lonely Planet/Tripadvisor/etc and you should be able to find good recommendations. Hotel laundries are so expensive that it's usually cheaper to simply buy new clothes.

I'd pack light enough to be able to move everything to public transport by yourselves ... using the subway/tube is fast and inexpensive. We make sure that we have suitcases that we can wheel by ourselves along with an additional bag we hook onto the larger suitcase. You can also either bring some 'throwaway' clothes (my mom's technique) to make room for souvenirs on the trip, or buy another suitcase prior to leaving there (what most international tourists do here in the US when they buy a ton of new clothes here - clothes tend to be cheaper/better quality in the US).

Have a great time on your trip.