I have both ARF's and kit built planes. For me, building is an end in itself. I like to build. I find it to be enjoyable where a lot of people don't. ARF planes offer the least investment to get going. But, as you may or may not know, there are some planes that can't be obtained in an ARF. So in the case you might want something that's not offered as an ARF, then building is the only way...unless you PAY to have it done for you. That option makes the ARF look even better from a cost point of view. Another positive aspect of building is...it will teach you skills you will need when it comes time to repair that ARF.
Of course if it turns into a pile of toothpicks I'm stripping the good stuff off it
...this WILL happen to you on a few occasions too...you do the same and in time you will have spare parts and hardware, if you should want to give kit building a try. This scavenging of parts will in time make kit building a more cost effective option.
Initially though, I would say the ARF is the way to go. Get's you flying quicker.