The Senate bill has a lot more detail to it from what I've read. For instance, it requires the FAA to implement this rule within a certain time frame - and also says that if the timeline is not met the requirement will automatically revert to 1500hrs for copilots. It includes multicrew experience and other operating experience such as flight in icing conditions before being employed as a first officer at an airline.
Of course the House version might be the one that gets included in any final bill or none of this could pass so nothing certain yet.