When you write "base," do you mean actually a base unit or are you refering to today's base/mobile models?
I ask this becasue many base models are no longer being made and manufacturers (Uniden, RadioShack/GRE) have moved to a base/mobile hybrid.
With that being said, the newest Uniden base/mobile models are:
The owners manual for the BCD996T reads that the antenna jack is BNC. Since the BCT15 is based on the same design, I assume it is the same.
The BCT15 is very similar to the BCD996T, but without out digital decode (APCO P25), only 2500 channels (the BCD996T has 6000), slightly less band coverage, and some other minor differences. The BCT15 has the BearTracker™ Warning System
(alerts you when channels normally used by public safety systems are in use nearby), where the BCD996T does not. The function and features of these radios are somewhat similar to the Uniden BCD396T, however these models have additional features, such as Location Based Scanning
(using a connected, optional GPS, you can easily listen to systems as you travel). The BCD996T is a better scanner, as indicated in the price (BCD996T $509.99; BCT15 $229.99).
You can see a comparison
of the BCT15 and the BCD996T in the RR Wiki pages, along with other Uniden scanners. http://wiki.radioreference.com/index.php/Uniden_Scanner_Comparison