Some have kept track of the rewards and I have seen one spreadsheet.  It showed that rewards are greater by continuing sustained attacks through to the end.

Things do change in the game and this was some time ago.

Thanks John!

This is interesting on a number of levels.

A similar question was raised recently, and John gave much the same answer.

However the advice to continue with sustained attack to the end , would seem to be at odds with what players actually seem to do, and also with previous analysis and conclusions, but as John also points out 'Things do change in the game'  so any advice that is blindly followed out of old news or blind habit may not be the best way to go.

 Either take the advice, or do your own test to find out what you think.

There would seem to be an advantage in one hits till the uber is vanquished where you can find out how much energy you need and not be left with excess hero energy,which wont matter so much if targetting more than one uber in sequence. 

Equally loading up the hero with  energy to do one final hit may not work, if reloading is needed any existing advantage of a one hit finish has been lost.

Historically,it was suggested that as there was no more bonus to be gained,after reaching the maximum, it would be best to finish of the uber in a final blow,this also has the advantage of saving time and the risk of having the uber stolen, which may be dependant on the current game parameters and the newness of the kingdom.

Returning again to old ideas which I believe are still valid, again its something you could test for yourself, the more energy used in killing the invader the more material that is dropped and supposedly the better the quality.

Also what about the energy cost? 

Lots of players are porting around and 1 hit killing L1 invaders and ghosts for white wolf, which isnt the most efficient use of energy, which could equally apply to one hit killing of ubers after gaining the  maximum 600% bonus.

Energy is somewhat easier to acquire than it was.  And there are many more Vikings: Game of Shopping players.  As a result there is now a scramble to kill Ubers during CvC and Fury.  If you are online when a number of Ubers have re-spawned during these events and there are few or no other players active you can still make kill runs in leisurely fashion.  Otherwise, however, at those times speed is more important than maximising drops.

It used to be considered the height of bad manners to intervene in someone else's Uber run.  But that convention is virtually dead.