The Pod HD series is designed primarily for live play of electric guitars. It lacks some studio features that the X3 series has, particularly a dry signal over usb, as well as some vocal and acoustic guitar support as built-in presets. It is also not straightforward to record Dual Tones, as it is in the X3. If you are primarily interested in studio work, and want to use the Line 6 usb connection as the recording interface I would go with the X3, either X3 Live or X3 Pro. These devices also have the advantage of sharing tones/presets with the Line 6 plugin, Pod Farm (in some cases the direct tone transfer is limited due to some Pod Farm 2 features that the X3 cannot reproduce). There is no Line 6 plugin that will reproduce the Pod HD tones.

Having said that, the Pod HD tones are far superior to the X3 tones. If you want to take best advantage of this in a studio situation you will need a separate audio interface to your DAW - one that supports multi-channel I/O (the UX1 is not it). With that you can connect the HD Pro Dry Out to one channel input, the HD Pro analog outputs to another (mono or stereo) input channel, and depending on the capabilities of your interface, record the dry and wet signals simultaenously in your DAW while monitoring the wet signal via the HD Pro headphones. After recording the dry signal you can re-amp using the HD Pro and the two independent channels of your DAW - one for output of the dry signal to the HD Pro, and the other to accept the HD Pro outputs as an input. This will allow you to avoid the feedback loop that you face with a single-channel interface.

Hope this helps.