Right it's the strainers and whether a muffler is present or not. Both 8 L same shell same hoops same key holder. 4157 may have more pearl or satin flame options than 4103 out there the 4157 will more likely have the muffler.
have owned both 60s snares and played both for years.
Still have the 4103.
The 4157 I recall had the mushier of strainer. The Renown strainer more positive.
An old Micro will back off but of course you can- if you can find and depending available and $- be replaced with the new locking repo Micro.
(or make a safety that loops nearest lug rod over handle when engaged (it's easy)
Both same 8 Lug same die cast hoop same Jasper shell
a 4157 will more likely have the muffler.
the 4103 likely will not have a muffler and it's not necessary. Both usually have Key holder
If you can get your hands on one or the other and that's the direction you're heading don't pass up either.
If a 4103 (or 4105 6L) renown strainer fails or is broken I'd still buy if the price was right. They all 3 seem to get rarer with each passing day
Right now at home the 4103 is my favorite snare. It's been my favorite out in the field (gigs) altho there it may be the 4160 side lightning brass altho if a softer pro jazzier style the 4103 would go to that type of gig too.
4103- is my favorite snare
with a Gretsch set
4160 brass is a little loud on the ears at home
perfect back beat tho for pop stage
4103, 4160, 4157,