No way. Not for me. In lv.100, you'll surely get better pokes with better moves/natured/ev's/hold items and such, but the opponents are FAR too dtrong. It's way hard fir me to get above 15 wins there. lv.50 is much better, everything is not as good, and is lowered a lot, but it's a lot easier, especially when it comes to gettin the silver sybol there.
I found 100 easier because they tend to have better move combinations, which the CPU rarely uses (Although it does have the AI to utilize them sometimes. Just not fully). With 50 I find it all a bit hit-and-miss.
Level 100 definitly, i beat it so easy with it, and if your lucky you will get the pwnage team from the start, which IMO is Milotic, Houndoom, Venesaur.
Level 100. I can't stand having to use weak Bug types and middle-evolutions like Grovyle in the Level 50 challenge. Give me Metagross, Salamence, Ludicolo, and all the other Level 100's any day.
Yeah, against the flow, lv.50. I know that in Lv.100, pokemon may have stronger moves, but still in this 50, your enemy may use such weak or useless move,IMO. Well, get my Silver Symbol in lv.50, though.