For larger tracks I tend to reach for the 2050 if the traction is average. If the track is slippery or smaller I go for the 1900.
Both are great choices for 4s. For most tracks the 1900 can get it done. Ty and Jim and myself all ran the 2050 at Silver State and felt it was great. I was only putting 3400 or so back into our 4s packs after a 12 minute main with 3 warm up laps.