I don't think the slg% are all that similar. Beltre was at .426 and .424, while Reynolds was at .495 (less than a full season) and .458. They move in a similar way in the chart, but the scale is fairly wide. Beltre had five full years of 15-23 homers each year, and that's with a LOT more balls in play than Reynolds has. The strikeouts are a major difference, as well.
I think Reynolds has a home run floor for a full season of about 25. (That could be accompanied by a .220 avg, and he could get benched if he struggles badly, so I'm not saying he's a safe pick.) Even with the strikeouts, he's bested that every year (at least in terms of his hr rate). I'd say the floor for Beltre was a little lower, maybe 15. Jmo, but that power gap looks wider to me.