For me currently, I lag a LOT every time I open my modded Minecraft. FPS for first 5 minutes is average of 6-10. After awhile things can get loaded and it goes to 30. And once in awhile there will be lag spikes.
But dang, that's a worthwhile trade off for around 200+ mods
Just curious have you tried Minecraft with the mod list you stated with any of the computers? The only way to expand much more is to get notenoughids and notenoughidstweaker, or else the block id / entity limit will be overridden soon.
Btw, I run 360 mods, which gives me 10 fps avg, but here are some you really wanna consider:
Anti-Gravity Mod (adds freaking moon-like planets in the sky you can mine into to get access to many raw ores, beware the gravity though)
Lycanites Mod (this is gonna make yo game a whole lot more intense. Definitely a must, and your world will never feel empty again)
Aether II (a whole new dimension and title screen, although the dimension is the one that's amazing. Lovely concept of an inverse Heaven)
Advent of Ascension (never feel bored again with all the new biomes you gain access to, as well as the mysteries, mobs and hidden bosses you may find in each one of them)
Orespawn (the classic pre-historic boss occasional spawn around the world)
InfernalMobs (small interesting pockets of mobs at cool areas like at lava pits that make collecting obsidian that much more satisfying)
Portal Gun mod (simple mod after the game Portal 2, very interesting application in the minecraft context. A must)
Flan's Mod (You'll need these heavy artillery from pistols to machine guns to tanks and helicopters in order to tackle this new world of powerful mobs from the list above)
the y50 and custom built seem to be decent machines, not sure about the mac tho XD I don't have it but, sorry if I'm bowing down to stereotyping here, I heard it wasn't too worth the cost in terms of cost to function
Mac's aren't to bad, my first ever modding and minecraft experience was on one.
But There was less then 50 I'm a bit worried especially considering that the friend with the mac has a short fuse and usually gets very confused and angry with such things.
But fingers crossed it goes well if not I can always try fast craft or something like that.
When it comes to Macs and performance, specifically in Minecraft, it's really about the specs more than the operating system. I'm using a 27-inch mid-2013 iMac right now (i7-4771 @ 3.5 GHz [up to 3.9], NVIDIA GeForge GTX 780M, 1 TB fusion drive, 8 GB RAM, dual-boot OS X 10.10 + Windows 10) and I average somewhere around 800-1,000 fps in vanilla Minecraft at maximum settings. I wouldn't worry about your friend's performance just because it's a Mac, so long as the specs are decent.