Beckham:
-better engine
-better passer/crosser
-world class set piece taker
- good ball striker but not a tremendous goal threat (position played a part)
Bale
- World class athlete with pace and strength that few could rival
- Better take on threat
- Better finisher and goal threat
Achievements are pretty similar: Bale has the 5 CL's (really 4 as the last one he didn't even play in) and 3 La Liga's, Beckham has 6 PL titles and 1 CL along with 1 La Liga. Beckham was the UEFA best in Europe choice in '99, but Bale was never going to rival that award because of the Messi/Ronaldo era he played in. Both had around an 8 year peak where they were at their best ('97 or so to 2005, 2011-18 for Bale probably). Bale more injury prone, but also one of the best big game players of his generation.
It's close I think. They played different roles obviously so it's difficult to really compare them as apples to apples.