As noted, the extra $1000 catch-up is personal and can't be split, it can only go into the account of the person who qualifies.
And there is one more factor I forgot to mention. If one plan is payroll deductions and the other plan is direct contributions out of pocket, the payroll deduction will save a little extra on taxes. Both reduce your income tax, but payroll contributions also reduce your social security and medicare tax withholding.
