I have an opportunity to purchase either or both of these lens for a Canon EOS DSLR at a reduced price. EF 28-135mm, F/3.5-5.6 IS USM http://consumer.usa.canon.com/ir/controller?act=ModelDetailAct&fcategoryid=149&modelid=7337 AND/OR EF 75-300mm, F/4-5.6 IS USM http://consumer.usa.canon.com/ir/controller?act=ModelDetailAct&fcategoryid=150&modelid=7342 besides the greater zoom capability of the 75-300mm, is there a hugh difference in these two lens in the real world? I am leaning on buying the 75-300mm lens but not sure if I should buy the second one as well. On a limited budget. Thanks in Advance.