Generally, for an E1 I would think not because of the additional processing overhead imposed on the link end routers. Both header compressions are oriented toward getting the most out of smaller WAN links. The foregoing noted, you could always experiment (assuming you can accept the experiment's possible impact to your performance) and see the impact in your environment.
Other things to consider, if you haven't already, insuring the voice packets are queued first. Insuring any voice signally packets are protected. Considering, if offered, the advantages and disadvantages of different codecs.