As stated above, morphine is the standard opioid.  Other preparations that are believed to act faster, have longer duration or are better tolerated as regards adverse effects, may in fact have little real advantage to offer.

Speed of onset and duration can only be altered by changing the route of administration. Immediate-release oral preparations take about 1 hour to work, whereas sustained-release preparations take 2-4 hours. 

There is little appreciable difference between different opiates in speed of onset and duration of effect.

There may be slight differences in adverse effects, though constipation is a side-effect of all opioids, as it is opiate- receptor mediated  both centrally and peripherally, with little or no tolerance to this developing. Nausea may be experienced by about 40% of patients on morphine, but it should be remembered that nausea can also be caused by pain itself.

Tolerance to nausea tends to develop quite rapidly, although some patients experience it with any opiate preparation.

(Taken out until I have learnt how to do Tables on web - having enough problems with plain text - Ed)