Children are a big deal. If your Church is important to you, and you wish to raise your children in the Church, it is best if your spouse were also Orthodox.
The hopping from one to the other is very confusing for children, and they wouldn't wish to betray either parent, and therefore, wouldn't really grow to love one Church over another....and they will most likely grow up not caring for either one, as neither was close to their heart.
If there are no children, it would still be best if both went to the same church, or at least belonged to the same Church. However, as noted above, and I know many such situations, that in order to keep the peace at home, one or the other spouse will visit the other spouse's church.