Few years ago, I was as skeptical as u when it comes to buying a phone using the mtk chipset. Yes, back then they had bad reviews and horrendous usability. Gps was my main concern (because I often travel outstation to unfamiliar places) and at that time, it wasn't gps friendly.

But these days, the Helio X20 had promising feedbacks, and in the end I just bought it (last year). Dude, it's superb. Gps locked in seconds, no lag even multitask a few heavy games, battery lasted at least a day's work till bedtime. Tried opening an autocad .dwg (2d) file and surprisingly, no lag/hang at all.

However, mtk versions have no/less custom rom builds (if ure into that) than the SD versions. Majority will state SD has better battery utilization than mtk.