Arrexis

Agreed. I just made up a saying "When WiFi is in the mix, your speeds they cannot be fixed"
 
OP, what modem and router do you have? How many devices connected to WiFi?
It's possible the router just can't keep up with the connections and all the devices at once or isn't strong enough to actually push gigabit throughput. There are alot of "gigabit" routers that struggle to do over 600Mbps or so.

Regardless of the ping, I would grab the fiber connection. Not only is it going to offer better speeds and most likely stability, but it will also open you up to speed upgrades in the future (if your provider wants to).
Heres to hoping they stop their bullshit and start offering actual speeds.

Oh you mentioned QOS, contact the fiber ISP and ask them if the SOHO-router they supply will offer QOS. If not, I would reccomend you aquire your own router with QOS if the ISP allows that.
In fact, I recommend using a non-ISP provided router to everyone, since the ISP provided ones are very often underpowered and lacking features. If you must use an ISP provided router/multimodem, see if you can put it in bridge mode and use your own router.

So just to clarify, the 2 and 5 Mbps were just for comparison sake and is not the speeds offered by your provider?
 
Technically there will be no significant difference in the speed they provide you, 5 Megabit is 5 Megabit. But fiber tends to have lower latency (ping/ms) and depending on your provider, better uptime/stability.

Having a fiber line is a good thing, since it can supply vastly better speeds than DSL is capable of, and has better options of increasing your speed.

Another thing to note, DSL is often asyncronous, meaning that your download speed is different than your upload. With fiber these speeds are often the same up and down.

Fair point, I've just experienced disgruntled friends with 100 Mbps lines complaining about steam "downloading at 12 Mbps!". So I just default to "multiply it by 8".
 
Also a fair point, I have the same type of DSL line, and very often, around 10/1 down/up is the maximum the DSL provider can deliver, and just as often the DSL provider is the only option. Personally my DSL provider is no longer maintaining copper lines as of May, but my street gets gigabit fiber come this fall. Might be a couple rocky months. ?