No, they aren’t. Buybacks push stock price higher, which also makes a difference for option values in a way that dividend don’t.
Also, they are efficient in that they defer the taxation to the point of share sale, but they are inefficient in that holding a stock for less than a year in the US taxes them at the much higher short-term capital gains rate.
Furthermore, the dividend is cash, it cannot go to zero without giving you a chance to realize it - whereas a stock can go to zero at any time (and many will likely do shortly). I was a small investor in a company that did a respectable 5X exit for shares of the purchaser. I was thus locked up for 6m, during which they did a stock buyback but later promptly went down by 80 percent for reasons unrelated to the purchase of the company I was an investor in.
What was supposed to be a nice 5X exit, turned to a meager 1.5X, and I was extremely lucky that the lockup ended September (that is, same year) because otherwise, for tax reasons, I would have been approx -0.5X (that’s all my investment and then half again) on a 5X exit — as I didn’t have any taxes profits in the following years to net again. (You can carry losses forward for tax reasons, not backwards).
Dividends and buybacks are similar when everything is hunky-dory but never equivalent.