4G doesn't quite live up to the 60Mbps advertised speeds as we topped out at 40Mbps. Around congested urban areas like London you can expect speeds to average between 10 - 20Mbps.
Real-world results showed there was little to separate EE, O2 and Vodafone in terms of raw download speeds. Three was slightly slower but you can still expect 10Mbps+ in most areas.
The networks take a different approach to try and attract customers. EE focuses strengths like widespread coverage and consistent high-speeds.
Three might not be the fastest but it is the cheapest and the only network which provides true all-you-can-eat data, so you don't need to worry about going over data limits. It is also the only network to allow you to use your allowance in the US, so if you're a frequent traveller this will prove invaluable.
O2 and Vodafone offer similar high-speeds and enticing add-ons. O2 offers subscriptions to Evernote and The Sun+, whereas Vodafone throws in access to Sky Sports Mobile or Spotify Premium.
Ultimately, it's going to depend on the reception. For many people in the UK, the only way to currently get 4G will be to sign up to EE as it offers coverage in areas other networks haven't reached.
Make sure you check every operator's coverage checker before signing up to a plan. Also take time to look at the benefits offered:
EE - This is the network if you need the widest possible 4G coverage and consistent high-speeds and you're not too interested in add-ons.
O2 - Only if you live in or around one of the 13 big cities and you want access to discounts through the Priority Hub and subscriptions to Evernote and The Sun+
Vodafone - Covers a third of the UK. This one is for sports or music fans as you get the choice between subscriptions Sky Sports Mobile and Spotify Premium.
Three - Not the fastest, but the network of choice for those who don't want to be constrained by a data limit. Also allow you to use your allowance in the US.