ojas, i don't have experience at the canadian gp, but i do have some experience at the USGP. i'll give you an out look on my experience. i think it really depends on a few things.
1. how many people are you going with.
2. what you wanna see (overtaking, brake action, straight aways, etc)
3. level of comfort. (i assume the stands are like the USGP=aluminum benches)
reason's why
1. if you go with a lot of people, i think it would be fun to buy a GENERAL admission, because you can roam around the entire track, (event is about 2 hours), so you can explore different turns, and different parts of the track.. the DOWNSIDE in my opinion, you might be far off the track so unless you have a good camera the pictures MIGHT be blurry cause these cars are FASTTTTT.... and you have to arrive early to get a good "seat" where the general admission designates fans.
2. last year, i bought a seat for the USGP, and this was at a "S" portion and i was able to see the cars very well, since they are in 2nd/3rd gear. if you do purchase a seat, i would say, try to avoid STRAIGHT aways.. cause these cars FLY by, and you won't be able to even take ONE good picture. that's why most of the typical overtaking spots at the MONTreal GP are sold out.
3. i don't know if MOntreal GP has the seats that some euro GP's offer, (one's with back support and some padded...) but for Indy, they had aluminum benches and they were pretty uncomfortable since you can't lean back... but if you bought a GENERAL admission, i think (i'm not 100% sure) you can bring a small folding chair... or you can just lay a blanket down and lie down on the hills. (if you arrive early.. first come, best seats)
i plan on going with a few of my friends, and we plan on buying general admissions. hopefully, its like Indy, cause Indy had a lot of good places to view the race for general admission.