NO!!! If it is extra large it takes more stardust to power it up. Example) normal weedle costs 200 + 1 candy, my extra large takes 400 STARDUST and 1 candy.. I'm still working on gym tests between the two after paying to get them to match their CPs together and testing HP difference now

If it is extra large it takes more stardust to power it up. For example: a normal size Weedle costs 200 + 1 candy, whereas my XL one takes 400 Stardust and 1 candy. 

I'm still working on gym tests between the two after paying to get them to match their CPs together and testing HP difference now