Sun Microsystems is extending its discount program for startups to Israel and the United Kingdom. It's a reminder that even a small business in Manchester faces a question mulled by corporate CIOs: Do we build on Microsoft or Sun?Some 1,300 companies in the United States, China, and India have signed up for Sun Startup Essentials since the program was launched a year ago. Membership brings discounted Sun software and servers, free technical advice, and free software such as Apache, MySQL, Perl, and Ruby On Rails. Sun also offers discounted Web hosting to overseas startups via new partner NTT Europe Online.

Sun points to a "significant increase" in venture funding and startup activity in Israel and the U.K. as reasons for expanding Startup Essentials. Sanjay Sharma, Sun's director of startups and emerging markets market development, indicated the program would be expanded when I talked to him in October. (See "7 Deadly Startup Mistakes.")

Sun's not the only game in town. Microsoft has a Startup Accelerator Program for up-and-coming software companies and a Startup Center for other types of new businesses. Those are two different constituencies, of course. Microsoft is grooming the former for partnership or acquisition and the latter to be loyal Windows customers.

Sun and Microsoft are competing for the hearts and minds of entrepreneurs with a goal keeping them as long-term accounts. In this respect, small business owners confront that decade-old question that many IT pros have chewed on: Unix or Windows? Sun or Microsoft?

To be sure, there are dozens of other options, including hosted services and Linux, but these are two of the biggest and most obvious. My advice to startups is to weigh the decision carefully, taking into account your in-house technical expertise, ambitions for Web site development, server applications, and mobile device/application needs. Because as experienced IT managers will tell you, getting onto a new platform is the easy part -- changing your mind a few years down the road, harder.