Excellent work ... both of you.
It's great to see you both enjoy this hobby so much.
Also an excellent idea to produce 2 halftracks in the same build, it's kind of neat to see them compared.
Excellent use of drybrushing and and weathering to produce dirty but not overly abused vehicles.
Couple of quick comments.
Lady's first - A little more pastel chalk around the lower half of the vehicle and the tires will really set this one off. Think about your own car and how dirty it gets on the lower half after even a simple rain or a drive on a gravel road. The second minor point is on the .50 cal, if you have a pin vice, it is a good idea to drill a small holw in the end of the gun barrels. Quick and easy but sure improves the look.
Gentleman's last - I'm not sure if it's the light, or the flash from the camera or not. But there is a silvering to your decals on the side. Did you apply them over a gloss coat and then apply a dull cote to return it to a matt finish or just apply the decals straight onto the matt paint? If it's just the lighting, ignore me, but if they are silvered you may want to try this technique to prevent that in the future.
All in all another set of fine projects from you two. A nice dio showing the M3A2 rolling past the abandoned 251 would look real cool.
What's next you guys ..... I look forward to them.
Happy Modelling and God Bless
Robert