London to Oxford Travel

What you might be seeing as the "Oxford tube" is actually a bus. It goes from London Victoria station to Oxford, takes about 2 hours, and costs 15 pounds one way (11 pounds if you're under 26 or over 60). It leaves every 10-20 minutes through most of the day. No need to buy tickets in advance, although you can.

The train takes about an hour and costs 26.50 at off-peak times (although you can cut that down to at least 5.40 by buying Advance tickets for a specific train). It leaves about every 10 minutes. The catch is that it leaves from Paddington station, so first you have to get there from Victoria, which negates much of the time savings.

For my money, the bus offers the better balance of time, cost, and flexibility. But check their luggage policy to make sure it's consistent with what you'll be bringing.

Trains to Oxford depart from London Paddington station (plus a few from Marylebone). You can't get from any London station to anywhere, it is specific stations for specific areas of the country. Victoria serves South and South-East of London, Paddington covers areas to the West of London.
If you are starting from near Victoria station, you will need to take the tube to Paddington, followed by a train from there to Oxford.

It will be cheaper to buy tickets in advance for London to Oxford. Website here: http://www.nationalrail.co.uk/

Bus is the best way from Oxford to Heathrow, because Heathrow only has connections into London. Oxford to Heathrow by train would involve going to Paddington and then doubling back on a train to Heathrow. Taxi would be much more expensive.
I don't know the pricing policy for these buses.

For a taxi you would be looking at £70 or so for a 'regular' car from Oxford to Heathrow by a local private hire firm. More if you need something bigger, executive etc.

For London to Oxford there are a number of consideration to weigh up; not clear for example whether you are near the stopping points for the coach services in Buckingham Palace Road (Oxford Tube or X90).

Also the buses from central London to Oxford are much more liable to be delayed by traffic than trains are to have delays. As others have said, it depends very much on whether you are staying near Victoria.

Thanks for the great input. Our lodging is a 7 minute walk from Victoria Station so it appears the question boils down to taking the 30 minutes to get to Paddington Station and the faster train, or taking the bus from near our location and experiencing potential delays with the traffic.

The trip from Victoria Station to Paddington Station is 17 minutes on the tube.

it appears the question boils down to taking the 30 minutes to get to Paddington Station and the faster train, or taking the bus from near our location and experiencing potential delays with the traffic.

That's it exactly. I don't have a lot of direct experience with the London to Oxford bus, but with other UK intercity buses, the schedules are usually padded enough to account for most normal traffic slowdowns you're likely to encounter. It's always possible that something really unusual could happen and you'll be delayed even beyond that - but that's a possibility on the train as well.

What might also come into the equation is where you are staying on Oxford - if somewhere on the eastern side the coach may prevent you having to travel out of the centre.

This is the direct bus service between Heathrow and Oxford. We used it on our last trip and found it quick, comfortable, and convenient. Much better than going into Paddington and out again.

I'd recommend the train from Paddington to Oxford instead of the bus from Victoria. More reliable and comfortable, probably faster even with having to get to Paddington from your lodging.