which will be best from Bsc nautical science and B. tech marine engineering according to their scopes

For decades there is a much larger demand for marine engineers. Demand goes from time where engine rooms were very hot and work was very demanding. Now you have a nice control room air conditioned and work is mostly done by contractors as ships are scraped as soon as they pass their warranty period. Also work at engine room is 8-17. Where before there were night watches, now that is all automated with sensors so you can sleep in your cabin when you are on watch and alarm will notify you if there is something wrong. Nautical officer position is very demanding in terms of sleep. Junior Officer has 8-12 and 20-24 watches on the bridge. But also from 13-17 he would attend to his safety duties or office work. When ship arrives in port, and for most of ships that can be every 48 hours, you are usually on standby 2hours priror to arrival and 2hours after departure and if your shifts starts then plus if it matches 6 hours on 6 hours off shift rotation you've done while in port monitoring cargo loading and discharge it is clear to you that very regulary youll not be sleeping for 24-36hours also youll be freezing outside or cooking. 2nd officer does 12-4 and 00-04 but he also has voyage planing ( that you are not permited to do while on bridge as you have to watch and navigate ) and office duties as well and 1st officer has 4-8 and 16-20 watch plus office duties, plus ship maintenance duties from 8-12 plus he does all cargo operations while in port so he is not on 6 on 6 off rota he is usually 12 hours on and then goes to sleep for 4 hours then back. if you are captain thats easy, you can become one in 15 years. so, my recommendation is to you go engine. salary matches positions on deck and engine 3rd officer - 3rd engineer, 2nd officer - 2nd engineer etc.

Go to these 2 links. I hope they can clear your doubts.

1. https://www.marineinsight.com/careers-2/what-is-the-difference-between-nautical-science-and-marine-engineering/

2. http://entrance-exam.net/forum/general-discussion/difference-between-bsc-nautical-sciences-b-tech-marine-engineering-8921.html

Good Luck.