Let me share my experience.
I bought a m120d01 around 2 months ago. I enjoy it a lot and fly 3 packs of battery each day. But I spent about 2k for parts now!
2X cannopy (34 each) 68
1X pairs of main blade (HKD 22 each) ~300
6 main shaft (HKD25 each) ~ 150
6 main gear (HKD 33 each) ~ 200
5 feature shaft (HKD22 each) ~ 110
1 tail boom (HKD 60) 60
1 cyclic servo (HKD 80) 80
1 tail servo (HKD 80) 80
1 ESC (This one is accident actually. My fault) (hkd 120) 120
1 pair of tail blade (HKD 17) 17
1 bag of screw (HKD 32) 32
1 set of rotor head (HKD 100) 100
1 set of swashplate (HKD 48) 48
1 set of linkage (HKD 22) 22
1 set of tail boom holder (HKD 22) 22
1 set of metal frame (HKD 25)
All are not spare parts. They are those I consumed! I now have around 700 spare parts on hand!!
I agree walkera's small heli is good looking and fun. But the parts is really expensive. FYI, main shaft for a 450 size heli (tarot) is around 10 RMB .... for 3!
It you can, buy a clone of align trex 450 (tarot) and a MCP-x (choose the one with spektrum dx6i). Then you can have indoor fun and a real good outdoor heli. According to other heli ching, a clone is ok for a 450 size rc heli. It is heard that Tarot make good clone of align trex 450. They have combo as well!!! BTW, I plan to have a 450 as well!
I think there is no wrong or right. But it needs to think twice. 450 size has its own fun and 120 size has it own unique feature. The only thing I complain about my m120d01 is parts are too expensive compare with 450 clone. But the main reason is there is no clone parts for such small size rc heli. If it has, I will never consider bigger size rc heli at this moment