After several years of being a REIN member, I decided to get my Realtor's license and chose Re/Max Real Estate.
Re/Max is more expensive, but it comes with instant credibility (in the eyes of the average consumer) and everything you need to get started. If you go to a minimalist brokerage, you'll need to figure out your own website, email, promotional materials etc, plus you'll be working mostly in the shadows of the larger brokerages such as Re/Max, C21, Maxwell, etc.
A comment above about creative deals - I put these through my brokerage regularly (AFS, assignments, vendor financing, etc.) and have not had any concerns from my brokerage.
If you're an investor hoping to market your own properties - it's true that the realtor disclosure form stalls many deals. And if you're looking to buy anything, you need to disclose that you are licensed as a Realtor and may use/sell the property for a profit. That also stalls/kills many opportunities.
If you have the drive, network and contacts to make this a viable business, then definitely get your license. If you're currently a full time investor, know that the focus to get your Realtor business off the ground will take time & attention away from whatever you're doing today.
If you're an investor looking to do a few personal transactions/year and collect just those comissions , I'd suggest finding a good realtor and setting up a business relationship for the purchases & sales in your portfolio.