So lets' say I start in January with 5% vesting after 1year, 15% after 2 years, and 20% every 6mo for the next 2 years. The signing bonus starts large and then shrinks proportionally to keep the TC constant. In my mind the only change is that my salary gets more "lumpy" at the end because I'm getting paid every 6mo instead of every 2wks.

So right before a vest I'm thinking "it's worth it to stay for 1 more week for 20% of my stock" but right after a vest the question is "is it worth it to stay 6months for 20% of my stock and 6 months of base pay?". That latter question seems the same whether my TC is cash or stock.