With out doubt, the majority of golfers with play better golf with a shorter driver. Most golfers should not have a driver longer than 44” or 44½” but most shop bought drivers are least 46”. The vast majority of my customers report greater consistency and confidence, whilst a lot report an increase in distance as they are hitting the "sweet spot" more regularly.
As far as swingweight is concerned - that is always a personal factor and can only be determined by trial and error. For some people the reduced swingweight of the shortened driver is actually beneficial, whilst for others it needs to be restored or even increased.
The one thing to bear in mind, as Ian mentioned, the shaft is the most important part of the golf club. Butts trimming with have NO detrimental (or permanent) effects on the shaft. If for some reason, the person did not like the shortened driver the length can be replaced and the original playing characteristics reinstated.