they both ****. I'v heard the infinity's and they are way too high for me. They also have no mid bass. as for the alpines, they are ok for use with hu power, but i'v had 3 pairs of alpine type-r comps and they all blow on me. if you have a budeget go with a pair of type-r's for now cuz you'll want more power pretty soon. other than that save your money and get you a decent pair of comps later on down the road that you can power with an amp.
I have the type S, and they are great you just have to put the trebble a bit down, sound pretty good, but is true you'll want more power soon, i have read in that the pioneer revs are great coax, check then if you can.