Roddy should be the better value, but I do think Julio is on the verge of becoming an elite receiver. To be an elite fantasy WR, you need hands, speed, size, freakish talent, QB, and a friendly offense.
With the exception (ironically) of Calvin Johnson, none of the top fantasy WRs play in a spread offense and get a lot more targets even if their team passes less frequently. Julio has all the other measurables, so I think it will happen.
I just am not confident it will happen THIS year, which is why I think he's being over-hyped and drafted too early for my tastes.