I like the Gùn because it's a cheap way to get a heavy PPC, but for an actual Capellan/Canopian BA taxi I like the Strider. It's faster, more durable, and not much more expensive. I wish it had a version with Angel and Bloodhound because I like to play with the TacOps Active Probe Targeting/ECCM/Ghost Targets rules - the Gùn has a setup with those but the rest of the package is lacking even compared to the average Strider.
I prefer the Strider D and its TAG, BAP, and C3S (and the ability to share the BAP targeting benefit over C3) plus accurate pairs of MPL and Streak 2s. Not the most spectacular setup, but it offers a good spread of utility for spotting and close-in support.
edit: If you're not playing by the strict 3150 IlClan list, the Owens F is probably even better. For some reason the Capellans gave it up after Late Republic and the Canopians never used it, but TAG, BAP, C3S, ECM, an LPPC, a couple of ERSLAS, and TCOMP is probably about the best you can do with that chassis and probably close to the best you can do for a stock IS BA taxi.