Often there is a part you don't see here where the lower valuation has a lower amount of money you can take. Would you rather sell 10% of the company for 80M on an 800M post-money valuation or 12.5% of the company for $125M at a 1B post-money valuation if you only need 80M to hit your growth objectives with a buffer and 2.5% of the company can likely be sold for a lot more than 45M once you need that extra money. It's also not smart to publicize you're taking less money as it makes you look more under pressure in the future and if it ends up being wrong to not take the extra cash you don't want everyone knowing you could have had $45M more in the bank. It gets even worse if the post-money valuation involves 15% vs 10% which can be viable as well.