I'm just wondering, in terms of technique, is it more difficult to learn the viola as compared to the violin. For example, is it true that it is more difficult to press the strings on the viola?

The C string on the viola is thicker and longer than the G string on the violin and therefore is harder to press and sustain. The main differences are probably physical as opposed to technical. For instance, to use the 4th finger to play a note on the viola is a tough stretch at first. Also the instrument is heavy and more difficult to play for long periods of time than a violin. I don't think there is a large difference between the actual bowing and fingering techniques until quite an advanced stage.

I picked viola over violin for two reasons:

1) I thought it was more useful to have C to F# at the bottom than all the squeaky notes up the top,
2) There a less violists in the world so I thought that I'd have more chance of playing in an ensemble sooner with viola and that happened to be true.

Also, the sound is deeper and richer.

Did you mean you picked Viola over Violin??

Yeah! Post now edited.

Although I agree in essence with Boo Radley's answer - that the stretches are larger especially for the fourth finger, the viola is heavier and therefore requires more physcial effort - I would (from a violinists perspective) say the viola is slightly, very slightly easier to play as far as intonation is concerned. You can be two millimetres out on the violin and the note will be out of tune, but with a viola you'd get away with that sort of error because of the longer string length. As far as general technique is concerned though, the instruments are equally as difficult.

On the subject of strings, it is no more difficult to press the strings down on a viola than on a violin.