It shouldn't be an either/or situation. Using more data is always a good idea. For example, look at Adam Jones. Last season saw him set career highs in runs scored, home runs, and batting average.
His past three years show an upward trend in HR/FB% and even an upward trend in SB. It makes sense to look at all available data, not just one isolated bucket. People (myself included) tend to forget that even seasons are arbitrary end points. Look at the work of a player in toto, not just buckets of data.