It depends on what you want from the machine in some ways...

If you think about it even if you are doing 4.5 miles both ways you are looking at 25 miles a week and thats just to work - let alone any other rides and other use.

The Dax and other similar type of frame mounts will do this without problem - but given that they are non commercial engines (aka not built by someone like Honda or similar) they can be more maintainence hungry and although unlikely to happen they are more likely to fail and leave you in the lurch than the commercial based kits. This is not to be critical of the chengine/frame mount engines, its a fact because of their type.

The rack mount engines such as the Stanton and GEBE have one advantage that they use commercial motors - and in the case of the GEBE belt drive with variable gears, the former uses a chain drive with optional gearbox. they are more expensive but then as the saying goes you get what you pay for..

I have had two GEBEs (one was stolen) and I have had no problems whatsover. I dont baby them and they havent missed a beat.

The choice is really frame mount if you like to tinker and maintain and for a reasonable price - or GEBE/Stanton etc if you just want a point and squirt machine but at a higher price point...

Welcome to the forum

Jemma xx