30 Mbit/s is the same speed, no matter if it runs over copper or fiber.
However, there are important link parameters other than link speed/pure bandwidth, so there may be differences. First, latency on fiber can be better than on copper depending on the line encoding - fiber requires much less elaborate encoding (see below) than e.g. xDSL. However, lower latency doesn't make the fiber faster but sensitive applications may respond faster.
Second, fiber's scalability is much better - in the future, you can just call your provider and order more speed. Speed on copper may be very limited, depending on the line length and quality. Speed on fiber is practically limited by your budget only.
Third, reliability or packet loss ratio is usually much better on fiber than on copper. Copper is generally susceptible to EMI (depending on cable type, cable quality, link length, and environment) while fiber is practically immune.
EDIT: in regard to "elaborate coding":
Fiber commonly uses 8b/10b line code with 20% line/bandwidth overhead, or 64b/66b line code with 3% overhead, but next to no time overhead or delay (less than a microsecond).
xDSL variants use OFDM/DMT and QAM encoding and modulation to cope with the channel's high attenuation/low signal-to-noise ratio. Reed-Solomon forward error-correction (FEC) is added to decrease the effective error rate, causing a transmission delay/added latency of a few milliseconds or a few thousand microseconds. Long lines also need to add interleaving for protection against burst errors, striping consecutive packets into each other - this causes significant, yet additional delay/latency in the order of 20 ms.
In a nutshell, voice-grade copper's low frequency bandwidth and its sensitivity to noise require elaborate encoding and FEC, which in turn significantly increase latency. Of course, when FEC fails and an error cannot be compensated, a retransmission is much worse than the usual 60 ms RTT for (long-line) ADSL.