I'm going to go against the grain here, and suggest you use the four stroke.

Why? Quite simply, because you want to.

What those above have said is certainly true...your trainer aircraft is meant to be just that....a trainer. Yes, by definition, it's more likely to be banged up, since you're gaining valuable early experience with it. And yes, certainly, 4-stroke engines are more prone to damage when crashed, and more difficult to repair.

None of that, however, changes the fact that, imo, your introduction to the hobby should be as much fun as it can be. If you're willing to accept the increased risk of more likely damage/more costly repair, then by all means, fly what you enjoy and build a trainer you think is cool.

After all...the cooler it is, the more likely you are to stay with it and learn more on it.