I'm using all day Firefox for front develop, an I have multiple tabs open. I don't have any issue of excessive RAM or CPU usage. Even I noticed that Chrome uses more RAM that FF . The actual instance that I have open to write it, with 16 tabs open, it's using around 300-400MiB and ~5% of CPU.
Also, FireFox for Android runs faster that Chrome (not because FireFox is faster that Chrome on Android, but because the ad-blocker does a nice work avoiding to load garbage), and the RAM usage it's keep at bay. I have like ten tabs on FF for Android and keeps working like if I had one open.
On any case, on Chrome and Firefox you can install a add-on called "Tab suspender". It allows to save ram, literally suspending tabs that has not been accesses on some time. Try it.
Also, FireFox for Android runs faster that Chrome (not because FireFox is faster that Chrome on Android, but because the ad-blocker does a nice work avoiding to load garbage), and the RAM usage it's keep at bay. I have like ten tabs on FF for Android and keeps working like if I had one open.
On any case, on Chrome and Firefox you can install a add-on called "Tab suspender". It allows to save ram, literally suspending tabs that has not been accesses on some time. Try it.
*edit : grammar