Applied vs Theoretical Journals (or venues)
This is not a direct answer, as I do not have that much experience with work crossing the theory/systems divide. I do have experience with the theory/bioinformatics divide, which is quite similar.

First, the publication venue should be chosen according to the intended target audience. If you believe your work is directly relevant to a community, you should publish it for that community. If it is only potentially relevant, you should probably publish it elsewhere.

I frequently read algorithmic papers published in theoretical algorithms, algorithm engineering, and bioinformatics. The fields have very different standards for what constitutes a good algorithmic paper. Proofs and analysis are the primary content in a theoretical paper. Experimental evaluation, if present, is considered secondary. The situation is reversed in algorithm engineering. As a result, a good algorithm in one field is often not that good in the other.

Things get a bit weird in bioinformatics. The algorithm itself is secondary content, as people are more interested in the problem you study and whether you have biologically interesting results. An algorithm is good, if it solves a relevant problem in practice. There are some bioinformatics papers with plenty of mathematical content, but they are exceptions. Proofs are seen more as technical details better suited to the supplementary material than as scientific contributions. Hence the reviewers rarely pay very much attention to them.