Is MBA through correspondence(along with experience)n better than regular one?

If you are planning to do MBA correspondence, then it's hard to find any option better than Symbiosis. Since, you are a working professional, therefore, if you can enroll yourself in some good MBA Part time program, then it's even better.
Apart from the above options, now a days a number of Post Graduate Certificate courses (correspondence) of around 1 year duration are being offered by very reputed institutes such as IIMs, XLRI, IIFT in specific domains. You can even opt for them if you want to do a short term course in your area of specialization. These are being offered through satellite communication in association with a local partners in many cities of India.
As far as the openings in this sector are concerned, you most probably won't be considered for jobs based on your MBA degree if you do it through correspondence. However, if you intend to remain in the same organization then doing MBA might prove to be a good option when you move the ladder up in your firm.
The filed in which you want to do your MBA depends on your interests. Operations Management is a very good field for folks like you who have a degree in Mechanical Engineering and are inclined towards Manufacturing & Services Sector.