The bike handle with a properly fitted harness might be better for your application. You will likely find it much less tiring. The loop works better for smaller or confined areas but the FS250 is a bit heavy. The Shindaiwa, my favorite, and the Husqvarna are also excellent choices.

I agree with canguy.

The bike handle and harness can be adjusted for nearly perfect balance and it's much easier to use for extended trimming sessions.

The loop handle isn't that bad but I wouldn't want to use it for any long stretch of trimming or for the larger/heavier trimmers.

+1 on the loop vs bike bars.

Any reason you are going with a FS250? They are more into the brush cutter league. You did say tall grass and brush, but was wondering if you could save a little money with an FS130 or 110. It made me think that since you used a loop handle in the past that you did not necessarily need the larger trimmer, but that assumes that you will be working in the same terrain that you did in the past.

I think the only disadvantages with bike bars is that it is more difficult to turn the trimmer on its side to edge a lawn and they weigh more.

Suggest one or more visits to local non-big-box sellers and try one on.