I have used both and so far I can highly recommend tecno although my current phone is infix. First,the good thing with infinix is that they have very good cameras unlike most of tecno cameras. The major problem I realised with infinix is that most of their internal storage isn't always matching with what is indicated in the details.Lately a colleague of mine bought infinix note 2 which indicated that its got 16gb ram while in real sense it had 5gb internal storage. This case rarely happens with tecno phones.
Also, the fact that, most of them have an inbuilt battery makes most people hate them. At times due to some carelessness a phone might fall into water and removing the battery immediately can save the phone. Only a small percentage of tecno have adopted to inbuilt battery.