It would be better to just transcode once at the exporting process.
Lossy encoding only happens once in both cases.
How direct import-export works: input file -> lossy format decompressor of editor -> filters -> lossy format compressor of editor -> output
How external codecs work: input -> external lossy format decompressor -> intermediate representation(lossless codec, can be just storing raw frames) -> IR decoder of editor -> filters -> IR encoder of editor -> external lossy format compressor -> output
Both options have only one lossy step - lossy encoder. Or technically two - also filters, but this is editor's intention.