I started out using the stock 600mAh 4.8v NiCD which came with my 6 channel radio (Futaba 6XASuper). I use only 4 standard non-digital servos in my trainer and safely got at least 4 flights of 10 minutes each on a single charge.

Once I got experienced and wanted to fly more, I upgraded to a 1100mAh 4.8v NiMH pack. I can put in about 6 flights per charge now plus the NiMH is a bit lighter than the NiCD pack was.

Now I have an electric sport plane and use a 3 cell 2100mAh 11.1v LiPo pack for the RX and motor. I get one 10 minute flight per charge. I can charge the LiPo on the same Triton I charger I use for my NiCD and NiMH packs but I had to buy an expensive balancer. I use a separate BEC for the RX and servos. I can program the BEC to output anything from 4.9 to 9.0 volts but 5.1v is the default.

Summary is NiCDs are the most durable and stand up reasonbly well to a bit of abuse. NiMH will have a higher capacity with a slight reduction in weight but can't tolerate charging abuses very well. They also self-discharge quicker than the NiCD but NiCD must be properly disposed of via a recycler.

LiPo offers the best combination of performance and weight but are expensive and tolerate ZERO charge abuses. You want to see your model (or home) go up in smoke? Overcharge a LiPo pack.

Best charger to use with a standard capacity NiCD or NiMH pack is your wall-wart charger which came with your radio system. I see NO advantage for sport flyers to run 6v packs. And 6 volts will limit your charger options.