There should be some level of balance between bat and ball in one-day internationals. However, once both teams play in the same conditions there can be little to quarrel about.
If there has to be a bias, it should slant towards the batsmen, as spectators will get more value for their money. Spectators want to see balls flying, not bails, and counting sixes is part of that experience.
Naturally, some grounds will provide conditions in favour of some batsmen and some in favour of the bowlers, depending on where in this beautiful game is played and the time of the year.
At any rate conditions will vary, so we need not lose too much sleep on this one. For example, early season conditions in England (June, July) with the natural covering of grass will present seamer-friendly pitches that are hard to replicate in other countries.
This will require a different skill set from batsmen and scores will vary. Bowlers have added all types of variety to their arsenal and it can be very difficult to standardise wickets to suit all. The pitch must complement the atmosphere at respective grounds, and many improvements in recent times have been in favour of the batsmen, from the big bats to the rule changes to the shortened boundaries.
So how can we check batsmen or test their true skills? The game has evolved where white ball teams are made up of more and more all-rounders. So those who bat and reap the rewards of good batting conditions could very well suffer on the other end of the same game when roles are reversed. This debate could go on for some time.