I'll admit, the HLBS stuff is not high on my list of things to buy, mainly because the list is rather long, but it does fill some holes (such as the BMP1 for second/third line units) even if the scale is slightly different. However, when I start doing more stuff in the African setting of Zaiweibo, the older vehicles will come in handy either as left overs from the Cold War or as part of more historical games (the Eureka Rhodesia range is tempting me into running some games showing the North/South Zaiweibo Unification conflict).
So Empress - I guess that HLBS is stocking their stuff just for convenience so honestly buy it from where you fancy buying it from. If you're also picking up a load of figures from them, adding a HLBS vehicle to an Empress order is going to save you postage. As for the T14, Empress has a quite long development process on all their ranges (which can lead to situations like the US Rangers last year where Spectre and Empress released at the same time) so it wouldn't surprise me if it was already in the works when SASM showed off their's.
The other thing is that for many people Empress's vehicle are a known quantity - I know the level of detail, ease of assembly and customer service to expect. I haven't picked up one of SASM's cast vehicles yet but I haven't been impressed with any of the 3D printed vehicles I've seen in the flesh.