From an employer’s perspective, a candidate is considered as good as the institute he or she is from. Truth be told for all practical purposes, there are only two engineering colleges in the country – IITs and non-IITs. Similarly there are only two b-schools in the country – IIMs and Non-IIMs. However good the other engineering colleges/b-schools may be but industry seems to always prefer the IIT / IIM brand over all else. The stream hardly makes a difference in the longer term. Unless you are sure of building a career in your core stream of choice, it really wouldn’t make sense to drop a year just to change your engineering branch in the same institute in my opinion. However, if you want to appear for JEE again and move to IIT next year, that may be worth the year drop but you should definitely take admission in whatever institute you have got admission in the current year to be on the safe side.
If you are looking to build a startup in the long run, it doesn’t matter what degree you have. Being an entrepreneur is about taking initiative & solving a problem. If you are passionate about something, go ahead and take the plunge. Just make sure you have done your homework and built a simple excel sheet with revenue stream & expenses to ensure you know what you are getting into and have yourself covered with regards to finances.