I'll offer them up anyway.
► First, I don't think the X-Terra 30 is out yet, but I might be wrong.
► I wouldn't be too concerned about it because most models do not have user-adjustable GB from the factory preset. At least not that works well. The White's Classic series do, but they were designed that way!
► The Classic III, ID and IDX or IDX Pro, (especially the III SL & IDX Pro) lend themselves well to GB tweaking with modifications. Many "turn-on-and-go" models available today lack any user access and/or control of the GB.
►.. The X-Terra 30 concept was for an easy to use model that also has less features. Specs on the '30' say the Target Volume only allows half the adjustabilty (1-10 compared with 1-20); half the fine-tuning for Sensitivity (1-10 compared with 1-20); only 2/3 the number of notch 'segments' compared with the '50', which also governs all the discriminate adjustment; a 3-Tone Audio compared with the X-Terra 50's 4-Tone Audio; no "noise cancel" (frequency shift) control; doesn't have the 'short-cut' for the All Metal Accept mode, and it only has one 'pattern' mode to customize. In addition, the X-Terra 30 has "standard" depth while the X-Terra 50 has "enhanced" depth.
In conclusion, I don't think anyone would be all that concerned to want to mess with the unit only to be able to 'tweak' the GB much at all since it wouldn't be that big a benefit in the overall picture.
Simply buy the X-Terra 50, which in my opinion, is going to be a hot selling model, It wouldn't surprise me if the '30' sales are so weak that they drop it down the road. The X-Terra 50 has a lot to offer for the $200 difference in suggested retail (US).
Monte