Paid RTW will likely earn enough points for elite status in many programs. I'm familiar with Oneworld's RTW, cannot speak to Star Alliance's. Obviously, depends on what your routing is and which program you end up choosing. BA's program is relatively easy to earn status with.

Is it worth it? Depends on what you're hoping to accomplish. You mentioned upgrades into first - those are extremely unlikely, even on a paid business ticket. Very few airlines even have real first class anymore, and nobody offers complimentary upgrades into their international first class. You might be more likely to get a operational upgrade into first with status if business class is oversold, but it's not worth basing your decision around that. Crediting to AA and earning AA status would offer the possibility of upgrades on their flights if you're flying domestically in the US, but your ticket would already book you into first class in the US on those flights, so that would only be worth it for flights outside of your RTW.

Paid RTWs, at least on Oneworld, should offer much more flexibility than award tickets. Some award tickets might require you to start from scratch if you want to make a change. The Oneworld RTW allows you to change dates even after you start the ticket for free (some airlines may charge you a service fee), while you can change stops for $150.

On the other hand, award ticket RTWs allow you to start anywhere for the same price (to my knowledge). Paid RTWs change their prices by where you start, and so starting in certain countries can be very advantageous, while more popular ones are prohibitively expensive.