For new development staff, I advise going big. That is, starting out with an organization large enough to support your growth and development as a fundraising professional. At the early stages of your career, it’s wise to work in a place where you have access to training and other educational opportunities to round out your technical knowledge -- such as, applying statistical analysis to your donor file --as well as to acquire some level of expertise in areas like nonprofit accounting and regulations governing charitable solicitation. Like any field, fundraising has its own specialized areas; planned giving and grant-seeking are just two. Gaining knowledge in these and other areas will make you an essential player in any development office.
But you will need to commit time to expanding your knowledge base, and it will be much easier if your organization supports your efforts -- and not just in theory. A large organization ($10 million plus), in most cases, is in a better position to underwrite the training you need and to give you work time to complete it.
As someone who benefited early on from week-long courses in planned giving, marketing, and major gift development, I can attest to the benefits of early-career training. It helped me immensely as I moved among different organizations and moved up the ladder.
Of course, if you opt for small organization, you can still access lots of free and low-cost training (check out the Foundation Center), but you will still need time off to do the training. The reality is that in small shops, the profit margin is slim, the staff is stretched, and time off for career development may be difficult to manage. In a bigger organization, you may feel lost in the bureaucracy and you may sacrifice some autonomy, but the payoff in learning will be worth it. And you will be a lot more valuable to the next place you work.