Can't tell the difference. Nice job on the reduction.
I know it takes a lot of time correcting poly's and such but it will be worth it. Again the tank looks good but in all honesty it doesn't have to look that good. When you render you can compensate with anti-aliasing even if you have to push the number upwards it's still quicker than having to many poly's that it won't even load. On my Roco tanks the more visable detail is there but again if i want to get really close to it i will rebuild it and use it as a seperate mesh.
A good habit to get into is reduce poly's as you build. Bandglue is a good plugin to get into.
I see your pipes look really really smooth. When i build them i start out with a 6 or 8 sided poly and extrude it, delete the ends and sub patch them. When they are subpatched you can keep smooth shifting them to make your bends. Reduce the subpatch levels before you freeze the tube. That way you do not have to make a tube with 40 plus to get them to look absolutely smooth. I can tell those tube's are pretty high poly's?
