@hugyzhug
There are two versions: cuteTube and cutelTube-qml.

As far as I am aware, the latter is more up to date and has more features*. I believe it's possible to have both versions installed at once but most people just have one**.

For any given piece of software, it shouldn't make any difference whether you manually uninstall an old version of a programme then install the new one, or automatically upgrade/update to the new one, except it should be quicker to do update. It's also possible you will lose certain settings if you uninstall something but often these are stored separately from the programme binaries, in which case you won't.

How to install qmlTube: (using built-in application manager)
- Open application manager
- Press the bar at the top and ensure the maemo.org "extras", "Nokia Applications" and "Nokia SSU" catalogues are definied and active. See wiki for info on repositories.
- Press "Download" (middle)
- Press "All" (top left)
- type "cutet" (search)
- press on cuteTube-qml
- check the check-box and press "continue".
... follow any other onscreen installation instructions.

For updating, as above except:
- swap Update (right) for Download (middle)
- there probably won't be many programmes to update so probably no need to type to search. Just select the one you want.

Right now, the latest version in extras is v0.8.2, In testing and devel 1.0.12 is available - careful of these repos though!

* , ** from what I understand, not from direct experience