Kevin, here's just some background information for you (the answer was already suggested by several of our colleagues).

The evidence offered as No. 1 is a written expert opinion or statement which the offering party has obtained. According to the German Rules of Civil Procedure, this expert opinion is viewed as "Parteivortrag".

The evidence offered as No. 2 is an expert opinion to be ordered by the court - and therefore, an "independent" opinion. The party offering this evidence wants to make sure that an independent expert opinion is ordered by the court if the opposing party does not agree with the offering party's "own" expert.

So, you can even use the same translation for both German terms.