LTE network provides a broad path to deliver different kinds of services through its network. I am considering two kinds of services as example, one is FTP and another one as conversational voice. FTP requires 100% successful transfer else file would be considered as partial/corrupted. In other case when two people having conversation packets carrying voice (VoIP) packets should be delivered on as it is, here re-transmission would be good solution to deliver packets since re-transmission would overlap the words and end user would get jitter. That's why FTP service uses RLC AM mode while conversation voice uses RLC UM transmission mode.
In essence, radio bearer carrying conversation voice would be having higher value of packet error loss rate compare to other radio bearers carrying ftp data.
There is another parameter i.e "Packet delay budget" associated with each bearer. This parameter tells how much delay for a packet can be tolerated because of congestion in the network or due to some other reason. If you see for conversation voice and real time gaming services, packet delay budget is less.
