Pros of 1815: manual wind, curved logo, luminous dial and iconic 1815 numerals.
Pros of Saxonia: outsize date, automatic but caliber which is more interesting to look at, nice black/silver aesthetic.
Cons of 1815: caliber which is a bit boring to look at, lack of the iconic outsize date.
Cons of Saxonia: very/too symmetrical dial (I prefer the off centred date of the Lange 1), not fond of the double indexes at 3 & 9 (hard for me to say why, but I find them too "straight" and, for whatever reason, I mind them less at 12 & 6).
Verdict: overall, I'd go for the Saxonia, but with reservations.