True, btc and eth are major coins, so this pair is available almost in every exchange which supports coin-to-coin trades. It really depends on rates and fees. For example,
Hitbtc has one of the best conditions with 0-0.1% fees. I think you should check some info about it, but at the same time don’t forget about other exchanges:
Binance has extremely large trading value,
Cex is good for newbies (btw, why you can’t trade coins there, this platform should support the pair?), Kraken offers professional tools, so you can check rates more effectively.
