Many things are different. Hit sounds depends on admins and they can upload any hitsounds they like
I use ETpro hitsounds on my silent servers and different admins use different.
Well the basic things which are good in silEnT are:
1. Hardware ban for cheaters.
2. Disable PM chat for level 0 users. Stop recruiting in PM's. (Optional)
3. Custom commands. Not possible in stock jaymod.
4. Map voting and TDM gametype for frag maps.
5. Mod based key for XPsave and banning.
6. Subnet bans with whitelist IP's to ban cheaters.
7. Advanced admin system. - No limit on user database. I have db size of 10Mb. In jaymod it causes XP reset randomly if reach user limit.
8. sv_cvar restrictions. Useful in absence of PB.
9. Auto move to spec after inactivity.. jaymod u can't.. admins have to babysit and move afk's..
10. Custom mute time.. mute different whinners for different time.. not possible in jaymod.
This are just few of many changes.. Jaymod has many issues which now a days are resolved in many mods. Jaybird is no where to find and hence admins are moving to different mods.