Here it is in brief. EE's lowest price is cheaper than Vodafone's lowest price, but Vodafone gives you more data for your money. O2 is perhaps the weakest of the three, with similar prices to Vodafone, but offering less data.
EE, Vodafone and O2 all have special 4G tariffs, which cost more than your current 3G contract. Three, however, isn't charging any more for 4G access.
That makes Three's offering the best on paper, as you don't have to pay any more to get 4G, or even switch contracts -- but coverage and customer service are still up in the air. Three's 4G network is also not expected to launch until December, so is little use if you're extremely impatient.
EE's cheapest 24-month tariff costs £26 per month, a rate that nabs you a meagre 500MB of data. Vodafone's cheapest equivalent tariff costs significantly more at £34, but comes with a much healthier 2GB of Internet. To get that amount of data from EE, you pay £41 per month.
O2 is somewhere in the middle. The cheapest contract that comes with a phone is £32 per month. To make things complicated, O2's deals depend on the phone you have, under O2's Refresh scheme which splits the cost of phone and airtime. The cheapest monthly airtime rate is £22, and phones range in price from £10 to £25, so you're looking at a minimum of £32. That cheapest airtime rate only gets you 1GB of data, though.
Calls and texts are unlimited across the board for all three networks, meaning the real focus is on data, which is what you'll be burning through using 4G's next-gen speeds, in any case.
A 12-month SIM-only plan from EE can cost as little as £21, but again, you'll only get 500MB of data, which is very little. Vodafone's cheapest is £26, which gets you a more reasonable 2GB per month.
Vodafone is also making 4G data unlimited for the first three months across all its 4G tariffs. That won't help you hugely in the long run if you're tied to a 24-month contract, but is a decent short-term offer to kick things off with.
O2's data offering is not very compelling. The smallest amount of data offered is 1GB, with 5GB being the pricey maximum.
From £37 per month (and possibly more if you're buying a fancier phone as well) gets you 5GB or 8GB of data if you sign up before 31 October.
Three's 4G is the cheapest by far, as it won't be charging any more for 4G than it already does for its 3G networks -- if you have a 4G-capable phone, you'll just get quietly moved onto Three's new network via a software update, without the need to start a whole new contract.
Three currently offers a SIM-only unlimited data plan for a mere £12.90 per month, which is miles cheaper than any other network. Sounds ideal, and hopefully it will be, but if you read further down you'll find there are a few areas in which Three's performance is not so stellar.
Vodafone and O2 haven't said how fast their offering will be, and with EE recently having doubled its speeds in some areas, it's set to be much faster than the other networks.
EE says the average speed of its network is 12-15Mbps, while those cities that have had the double-speed upgrade reach a pacey 24-30Mbps average download. Three says its LTE service will achieve speeds of 14Mbps.
Here's where EE is definitely winning for now, having had a long run-up in which to extend the tendrils of its next-gen coverage. EE is available in 100 UK towns.
O2 kicks off in London, Leeds and Bradford, and says it'll have 4G in Birmingham, Coventry, Edinburgh, Glasgow, Liverpool, Leicester, Newcastle, Nottingham, Manchester, and Sheffield by the end of the year.
Vodafone launches initially only in London, with Birmingham, Coventry, Leicester, Nottingham and Sheffield following.
Three's coverage is also just getting started. By the end of 2013 it aims to have Birmingham, London, Manchester and Reading covered, as well as Oldham, Dudley, West Bromwich and Wolverhampton. Over the course of 2014, 42 other cities will be added to the roster.
Cost and data allowances are the deciding factors, but the networks are also throwing in a few bonuses to sweeten your 4G deal.
Vodafone chucks in either Sky Sports or Spotify Premium for free, for six months on the cheapest deal or a year on the more pricey deals. EE gives you a free cinema ticket each week and free music streaming from Deezer if you're paying £41 or more.
O2 also offers a musical incentive, with a free year of music and video streaming from O2 Tracks. As an O2 customer, you also get early bird priority booking to sporting and musical events.
And if you're after a 4G tablet, O2 is also the only network that will sell the new Google Nexus 7 Android tablet, costing £320 from 13 September.
So which do I go for?
Right now I'd advise avoiding every operator, as the UK's 4G situation is still unfolding. With coverage still so sparse, there's every chance that committing to one network now would see you stranded without the fast data you so desperately crave.
Are you keen on 4G or would you rather make do with cheaper 3G? What's the best 4G network -- and what's the best 4G phone? Tell us in the comments or on our Facebook wall.
This article was updated on 29 August 2013 to reflect up-to-date prices and details. Additional reporting by Rich Trenholm.