Rdio (pronounced arr-d-o) is now available in the UK bringing yet another music-streaming service for you to try or appraise.

The newest player on the block, it hopes to take on the likes of Spotify, Deezer, WE7, and others to convince you that its the one you should be using.

We look at some of the differences between the king of the pile and the new challenger, to see what's what.

Signing up?

At the time of writing (3 May 2012) Rdio comes with a seven-day free trial that allows you to enter a few details or your Facebook login and get going straight away. The service is easy to setup, web-based so you don't have to install anything, and doesn't require your credit card. After the seven days you will have to pay a subscription if you wish to carry on listening to music. The Spotify service can be used free of charge forever, because there is no cut off time.

With Spotify, if you want to sign up to the 30-day free trial of the Premium version it does require your credit card from the start. If you opt for the free model you don't have to give you credit card details, but you will have to listen to adverts and be limited to some of the features you can access.

In both cases you will need a Facebook account to register for Spotify.

How much do they cost?

If you are willing to pay both offer £4.99 and £9.99 subscription packages. Both £4.99 packages give you only web or desktop access on your computer. If you want to play music on your mobile device, such as your phone, the iPad, Sonos or Roku, then you'll have to upgrade to the £9.99 package.

Both services can be used abroad, although Spotify does limit its free version to just 14 days - more than enough for that holiday you are planning.

What can I play my music on?

Spotify supports a number of platforms: PC and Mac, iPhone, iPad, Android, Windows Phone 7, BlackBerry, Symbian and even Palm. You can also get Spotify on the Sonos music system.

For Rdio the list is just as big. You can get Rdio on your browser, PC and Mac, iPhone, iPad, Windows Phone 7, BlackBerry, Roku, and Sonos, but Symbian and Palm users miss out (they are dying platforms anyway).

Rdio's ability to play the service through a browser is its biggest feature for us, especially if you want to use the service at work and aren't allowed to install any additional "non-approved" software on your computer. You will need to have the browser window with the player open though.

Spotify and Rdio also let you download music to your mobile device for offline listening. Handy if you are about to board a flight or know that you won't have the internet where you are heading. 

What features do they have?

The features the two music services offer are very similar. Both let you create playlists, both let you search music in their catalogues, and both have a very strong focus on the social elements of music sharing and discovery.

Rdio's Twitter-like follower approach is a lot easier to grasp straight away, but once you understand the social elements of both there isn't much between them. Both let you share what you are listening to, both let see what others are listening too.

It's very much like the difference between choosing Canon over Nikon for your DSLR, you'll soon know by playing with both for seven days which one you like, and because both offer you free trials you can do just that.

Where Spotify wins out is its new apps feature. Recommend listening by magazines services really are good and helpful, as are apps like Moodagent that play music according to the mood you set it. Rdio doesn't have anything like this.

Who has the best music catalogue?

This really comes down to who you listen to, but on the whole we've found that Spotify is more likely to have what you want. That's an incredibly sweeping statement, however on a very rough test of searching for artists in the two services we found for us, Spotify has more.

We searched for everything from Queen, to Bob Dylan, The White Stripes, The Presets, Rolling Stones, Eric Serra, and many more.

Interestingly Rdio opts to list the tracks even if it doesn't have them, while Spotify just returns a blank result.

Of course Rdio has tracks that Spotify doesn't have and vice-versa. If you want to listen to Pink Floyd's Dark Side Of The Moon you'll have to sign up to Rdio for example.

As with all competing services this is likely to be the case time and time again as the record companies sign exclusives. There isn't much you can do about it sadly.

Both have notable omissions like The Beatles and a lack of movie soundtracks beyond what is in the cinema right now.

Conclusion

If you are restricted in your ability to download any physical software on the on which machine you plan to listen to your music, then Rdio's web browser interface is the one for you. It's really easy to use and great if you are someone that likes music, but wants to be able to fire it up on other machines - say at an internet cafe.

Rdio's music catalogue is good, but for us still lacking, especially from a UK perspective.

That's likely to change over time, but for now, unless you are desperate for a few tracks from Pink Floyd or Bob Dylan, then Spotify will probably suit you better.

Combine that with a wide range of ways to listen to Spotify and the wide range of apps within the service to boost your listening experience, for now Spotify is still the one to go for.

What do you think?

Let us know how you get on with the two different services and what you like about the different services.