Both these branches of engineering are completely different from each other. Have a look at their respective scopes below-

Scope of Mechanical Engineering
Mechanical Engineering covers aspects like design and testing among others. The job demands supervision and planning of live projects related to thermal power plants, nuclear stations, generation of electricity, etc.
There are employment opportunities for diploma holders who have practical knowledge of working on fields like testing of machinery etc.
The emerging fields in this area include renewable energy, automobiles, quality control, Industrial Automation, Mechanobiology. These are going to increase manpower in the work profile of mechanical engineering and would offer employment opportunities.

Scope of Civil Engineering
The construction and infrastructural development projects including town planning are on the rise in the coming days and will demand more domain specialists.
In search of comfortably safe homes, better roads and standardised living, the demand for civil engineers are to raise more.

Now you have to decide your area of interest. It depends on you which field you choose to work. There is nothing like more or less good; you simply cant compare both.