Oyster Card: Simply put, it is a "credit card" style of travelling. You purchase the card from the well-marked ticketing machine at any station and you pay as you go. It cost five pounds for "using" the card, which is refundable when you leave (You take it to a ticket counter at the end of your trip and they give you back the five pound in the manner you paid). Then, you just load on how much you want to use at a time. You add money in the same type of machine you purchased from, just click the desired buttons, much like an ATM card and hold your card to the verification strip. I started with ten pounds per card. Mind you, that is five pounds to "rent" the card and ten pounds additional for travel, so fifteen pounds. (It was enough money for about 4-5 one-way trips depending on where we went. We stayed in Zones 1 and 2.)
The pros: You get the best value on travel costs. They charge you the going rate of your journey from place to place at the time you travel. Pretty simple. If you are only travelling a little per day, this might be a good alternative.
Cons: You have to put more money on it when you run out which might be often if you are travelling a lot. Also ,another con is that you have to stand in a pretty long line most of the time if you want your end refund. Bad, if you are running late. You might end up just leaving the five pounds in London.
Just FYI: You can see how much you have left on your card every time you exit a subway station on the exit ticker where you put your card in. This is very helpful so you don't get caught without money left. I didn't realize that helpful hint until the third time I exited since I was just trying to figure it all out.
2 for 1 card: This card is a great way to go if you will be in London a week, but it can be just as advantageous if you are there only a few full days. You have to get the actual ticket at one of the National Rail places. The other stations are not the right ones and will not work as a 2 for 1. There are National Rail Stations all over, but just check for the nearest one to where you will be staying before you leave. We got ours at Waterloo. You pay approx. 8.36 pounds per day for zone 1-2 and then you get unlimited transportation in the areas you choose (I recommend zone 1-2 since most everything is there). This pays for itself if you do the attractions in the book (the book you can get at the Rail Stations or else just download the ones you want to go to online. I found it easier to download the ones I wanted before I left so I was not stuck filling out the forms at each attraction. Plus, I hear that they can run out of them.) Download them here: http://www.daysoutguide.co.uk/attraction-types/2for1london-list.aspx
This is only good for adult passes. If you are travelling with kids, then it may not
be the best value.
Consider this... I bought two adult cards for 8.36 each one day, so total of 16.72 and then we went to the London Dungeon. On our 2 for 1, we saved 25.20. In this case, we received free transportation all day for both of us and saved 8.48. The same thing
when we went to the Tower of London. Cost was the same 16.72 for the day travel pass and we saved 22.00 on the 2 for 1. So again, free transportation and we saved 5.28.
Pros: If you find the National Rail and make a purchase on day one, (the first day of your visit) then you do not have to worry for the rest of your trip about adding more to an oyster card. If you will be using the rail a lot, you can save a lot of money. Some argue that the Oyster card is cheaper, and it may be if you do not do any of the attractions, if you are touring around and jumping on and off the tube, this is the cheapest alternative in the long run.
Cons: Finding the National Rail line the first day when you are probably tired from a flight. If you lose the card, you can lose several days of travel. Some places do not allow you to pre-book them with the 2-for-1 online. So, in our case, we wanted to do the Rib Voyage since it looked amazing, but we could not pre-book unless we called them from the US. As you can imagine, that could have been more for the phone call and then giving a credit card on the phone did not work for us. We headed there the first day, but they were already closed since we were in late. We had so much on our schedule that we never made it back... Hopefully next time.
You can be crafty and save a bit of money if you want to do some days. The days that you will be going to attractions, buy the day pass 2 for 1, and then use Oyster card the other days. It will save you money, for sure, but the headache that comes with it can be a pain for your trip. If I had brought a passport photo, I would have just done the straight seven day 2 for 1 Travelcard.
*So, about that passport card I mentioned: What no one told me, nor did I find the information on my internet search (probably just did not understand what it was saying at the time) is that you must have a passport size picture to get more then a one day pass. So please bring one along to get the seven day pass. You can find a photo booth at the stations, but why? I found some of the booths charge five pounds each, at home I could have bought one for $1.00 or used an passport one that I had left over.
**Take note of the pictures above of the Travelcard and the Oyster card. Actually, print them out! That way you can just show the person at the National Rail station the one you want. The Travelcard must look like the one above to work for the 2 for 1 deals.