I am not a chem major, but I do have some advice. I have been a PC owner for my entire life. I strongly suggest the IBM Lenovo over the DELL, definitely. The IBM Lenovo has a shell and system design only comparable to the Mac. I own a PC and a Mac. I use my Mac in order to test multiple client software environments and need to be able to easily shift to multiple environments(I can do this and do with my pc by using VM Ware and the Vista's Aero, AWESOME). As the other post suggest you can do this with fusion, but if you have no real interest in using the Mac OS then there is no real need to pay the Mac premium to just own the Mac when you will be using these environments most of the time (Windows). Thinkpads are Lenovo's business line of laptops and they are built nice (not as pretty as the Mac or the Dell but what it lacks in looks it definitely makes up in design, keyboard feel, layout and performance. My personal opinion is the IBM. Do not be fooled by the Mac it is sleek, but its shell does add some weight and takes some screen size from you as the Mac is 13.3 ibm 14.1 they weigh a tad less.
Hope this helped good luck,