My personal recommendation of the three you have listed is the Tippmann 98. It's durable, there are lots of parts, they've been used as rental markers for the last 15 years due to their durability. They just work. If you're using CO2 on the markers, I'd say just stick with the 98.
Now, if you're using HPA, you may want to start looking into higher end, used, electro pneumatic markers. In the $150 price range you can find something decent with a little bit of searching. The real catch is that you then need a faster hopper, etc. so you'll end up spending more.
For barrels, length doesn't yield better performance. You want a good ball to barrel fit that optimizes the gas being used to propel the ball through the barrel. This optimal size is dependent upon the paint size at your local field. Bear in mind that Tippmann has it's own thread sizing or barrels. Most other markers use cocker threading these days so if you ever get a higher end marker you'll basically also need to buy a different barrel or barrel kit.
For barrels you may want to check the Buy/Sell/Trade section of the site to see if anyone has used barrels for sale. If you're buying new, Lapco and CP put out a good product. I'm not sure if Inception has barrels that are threaded for 98's but you can email Simon and ask. Their Stella barrels are top of the line.