www.hashnest.com is actually good I have about ½ a btc there.
No one else is worth it in my opinion.
Why is that? hash nest builds s-7 s-9 L-3 since they are bitmain.
So they did not and will never pay retail for the gear they use to mine.
Yes you can lose money with them but I like them for the most part.
the avalon 741 with a rasp pi is about 900 and a psu it is about 1050
you mine about 7.5 th
hashnest will charge you about 1598 for the same hash
but hashnest will charge you 8 cents a kwatt and you will be using 20 kwatts a day or 1.60 a day
the avalon 741 will use 30 kwatts a day so at 10 cents power 3 dollars
in 300 days 480 in power vs 900
no risk of down time with hash nest
so if you weigh the two the avalon looks better for the first 200-300 days after that the s-9 from hash nest may be better.