Standard answer: Get both!
That's what I wound up doing...
The downsides of the AUG are that parts are spendy, mags are spendy, and extra barrels (which you know you want) are spendy. It's painted-on finish is also prone to wear, especially around the charging handle.
The upsides are that it's stupidly simple to clean and maintain, it's accurate, and with some training/practice you can do mag changes and drills as fast as an AR.
The downsides of an HK94 are that it's finish is like the AUG's; mounting a scope can scratch the finish. Also, it's a real PITA to clean if you're anal about any carbon anywhere on a rifle after you've cleaned it (as I am).
Upsides are that mags are pretty cheap, compared to AUG's (Tapco's running a special on stick mags right now), it's recoil is even less than an AUG's, and they're just so...smooth to shoot. Really, it's like...I don't know...it sort of feels like squeezing a tube of grease or something. It's not sharp at all. Also, there's a fair number of good HK smiths out there if you want work done to it (getting a real flap mag release installed, having a 3-lug barrel installed and a fake can attached, etc), but they're pretty spendy and backlogged these days.
Also, converting an HK to be sear-ready won't really diminish it's value. If anything, it might increase it.. I don't know what's needed to make an AUG registered trigger-pack ready, so I can't comment on that.