Just wondering what people would go for, seeing as this is a British forum I think the vast majority would be F1, (like me) but i could be surprised.
For me the Indycar series is perhaps a purer comrison of drivers, as the cars are all built to spec, engines are all supplied by one manufacturer (a bit like A1GP), and the varied tracks do make it interesting. Ovals do have the crashes going for it, but a uniform turns are a bit of a turn off, its good they race on other types of circuits. Indycars Im sure posess an ultimate higher top speed than F1 cars as well.
However what makes F1 better for me is that it is in my opinion the pinnacle of 4 wheel track motorsport (not wanting to anger the Moto GP and WRC fans out there!). The best drivers in the field do end up in the faster cars, and technical innovation spices things up a bit - and said innovations trickle down into other series and eventually road cars. Plus the F1 car is faster than an indycar on all but the longest straights - they may have a lower top speed but acceleration is far superior, lets not mention what would happen in a corner!
They both have their individual merits and its difficult to directly compare them apart from them both being forms of open wheel racing.
F1 is the peak in terms of technology and its worldwide appeal.
Indycar is far more focused on good racing, technology is a lot more primitive, but open wheel on ovals offers something very different to what F1 offers.
F1 cars are quicker around corners than Indycars simply because the current crop of Chassis(IRL era) are built for ovals. They dont have anything like the levels of downforce F1 cars have even with the current restrictions. However on superspeedways IRL cars reach >230 mph, which F1 cars dont even on Hanger Straight.
Personally if I had been given the choice of Indianapolis or Monaco on May 24th, I'd have been in Indy.
I agree that they are difficult to compare, and while both have some good races (Melbourne in F1, Chicagoland in IRL) they also have some dreadful ones (Milwaulkee on Sunday night was a snoozefest).
The thing I prefer about Indy Car is the fact that the drivers are more approachable. The majority are on Twitter (as I found out last night!), and the coverage on the website is superb. Not to mention blogs and other things that let you learn about the drivers, as they're not protected and limited by their teams.