I would suggest BITS coz U will get a B E there and it is better than IIT-G which is quite new !
						

							
Hi
BITS Pilani is a highly reputed institute considering its prior achivements. 

    
According to the Asiaweek magazine's rankings of Science & Technology schools in the Asia-Pacific region BITS Pilani, Pilani campus was on the top  in Asia and Top 5, in the year 2000 in terms of Student Selectivity. (UNESCO Science Report 2005(makes use of these rankings).
    
Annual rankings of Engineering colleges in India have been published by  magazine since 1997. BITS Pilani was consistently ranked in the Top 5(1997-2004). BITS opted out of the rankings in 2005-2008 because of a pending court case between BITS and But in 2009, the institute rejoined the rankings, and was ranked 7th in the list of top engineering colleges in India and it was also ranked as the best privately run engineering college in India.
    
Business Today lists the university in its top 20 Wired Organisations of Asia
    
Government of India's National Assessment and Accreditation Council (NAAC) rated BITS as a five star Institution for the period ending February 7, 2007. BITS has scored 82.55 out of 100, higher than comparable public universities (with a five star rating and a focus on science and technology) such as IIT Delhi(79.5),IIT Bombay(79.6),IIT Kanpur(81.2), Anna University (75.7), Bangalore University (77.05), Jadavpur University (77.35), Mumbai University (75.05), Pune University (78.55) and Roorkee University / IIT Roorkee (79.2).

So, if u compare it to IIT Guwahati , its definitely a much better institute, moreover Chemical engg. has got varied scopes in India and is one of the evergreen and desired branches. IIT Guwahati is also a good institute but its still more in the process of its development.