Compare bonus and salary structure.
A bonus is not equivalent to salary of the same size, because it is contingent. Weighting the target bonus by the probability it actually pays in full converts it into an expected value that can be compared with a flat salary. Two figures then matter: the guaranteed gap, which is what you lose every month if the bonus does not land, and the expected gap, which is what the bonus structure is worth on average.
Probability-weighted compensation
Target bonus = base x bonus percent; expected bonus = target x payout probability; expected total = base + expected bonus; guaranteed gap = flat offer - base
Bonus and salary are usually taxed differently, and bonuses may be subject to clawback or continued-employment conditions. Check the offer terms and take advice where the difference is material.
Ask what percentage of target was actually paid in each of the last three years. Discretionary bonuses tied to company performance commonly average 60-80 percent of target; individually controlled commission can be higher, and start-up bonuses much lower.
Because base salary sets your mortgage affordability, your pension contributions, your severance and the starting point for every future raise. A bonus does none of those, so a large expected value built on a low base is worth less than it looks.
When you control the outcome and the upside is uncapped — sales roles are the clear case. When the bonus depends on company-wide results you cannot influence, the flat offer of equal expected value is strictly better.