If I am not mistaken, I think you mean the unity amongst the people present at the specific Mass, and not amongst Catholics as a whole who attend different liturgies.
I don’t think so in regards to the former. I think the unity amongst those present is just as strong (or weak) regardless of the form on the liturgy. It depends on the people present. Anyway, we gain our unity as the Body of Christ through our communion with the Head of the Church, Jesus Christ, and His vicar on earth, the Pope of Rome, all professing the same faith and receiving the Holy Eucharist, the Sacrament of Unity.
As for the latter, I don’t think it causes disunity. My old parish offers both and there was no disunity that I could disern anymore than there is any less unity between those who go to the Mass early in the morning with little or no music and those who go to the Mass where the choir sings.
The Church as a whole has always had a diversity in liturgical rites without disrupting the unity in worship found in the substance of the Mass/Divine Liturgy.