wouldnt be majorly knowledgeble on the subject but the little i do know is that neither hp or acer have had a good rep. for quality of build in the past. However, they are still within the top 4 as regards the biggest laptop manufacturers.
I bought acer on the basis of the spec relative to the price....and also seemed to be getting the feedback that they have not suffered as much on the build quality in the most recent years...