We started with powder coated karts and washed them after every day out and sprayed with WD40 or similar. Lanolin was good but became messy. Easy to do without a pod. If you are looking at a pod, go stainless as most of us tend to leave the pod on and the keel tube doesn't get rinsed unless pulled right out. With a non stainless kart, the keel tube is the main part to rust if not washed regularly.
The chassis's all weigh about the same.
Performance wise, the chassis type does not seem to make any difference.
Maintenance wise, run a spanner over the bolts occasionally and pump the tyres up. Tyre pressure is critical. The rims are rated at 30psi and will distort if over inflated. Socially, I run around 30psi and race days, 32-35psi in the rear and less in the front. Some run much higher pressure and increase the risk of a blowout.
Don't wash the sail unnecessarily as they have a coating on them to water proof them. If they get wet, hang them up to dry so they don't get mildew on them.
I run steel bearings straight out of the box and do not clean the grease out. When they are too worn or seized, I put another set in (eventually!). The karts come with stainless bearings which are a bit dearer and don't seem to have any advantage.
Repair wise, any of the chassis types can be welded if required.
Chrome moly karts have a stainless floor and seat hoop. The full stainless is all shiny and look better. Once you put a pod on they all look the same.
Blokarts can be ordered with either fibre glass or carbon fibre masts or a combination. The strongest sections must go on the bottom. If you go carbon straight up you move to performance in competition but you don't get stuck with a $400 mast that you may not use. It is about $300 extra to buy ultra carbon straight up.
When buying a ratchet pulley, go for the 57mm (Harken or Ronstan) as they give a lot better gain and will last longer. Blokart have a 32mm.
The new sail bungee straps can be tied shorter to tighten the tension if required. I find the standard straps adequate.
Both blokarts hold their value well.
We run stainless chassis now with full ultra and a carbon second and crane. In hind site, it would have been better to start with the best as you only buy it once.
Check out Perth Blokart Club if you are planning to race. Their site is:
www.perthblokartclub.com.au/They have their state titles soon.