If you don't have revenue or customers and just and idea, 25% each. Your idea isn't worth anything without execution, market fit and customers - and equity is about the upcoming years of risk, turmoil and pain going forward in lieu of compensation and being a "partner" is about being in it together. If you have money and would rather pay them, - then treat them as employees and find some charts on how much to pay early employees. But when you say partners - be partners.
If you have customers and revenue then you need to take a look at how much value they bring and how much they (may) contribute to your success.
I love this: http://paulgraham.com/equity.html