Basketball-wise, Beal is better in the half court. LaVine is better in the open court. Rule of thumb is that most playoff games are won in the half court. When comparing players with similar talent level, always gimme the better half-court player. I'm very low on LaVine's BBIQ.
In terms of asset management, LaVine is 2 years younger, plus his max will start at 30% of the cap (instead of 35%).
All in all, imo Beal is a better player. LaVine is possibly a better asset.