Late to the party but no-one highlighted the primary difference between the DS218 and DS218+.
The + models use Intel processors; in this case a Intel Celeron J3355 vs a Realtek RTD1296 in the non-plus. The difference is important if you're concerned about 3rd party software compatibility; if you're only running the included DiskStation/ Synology suite it probably won't matter to you. No doubt there's other differences but I stick to Intel if it's an option.
I've been running a DS216+ for >2 years with little to no issues. My biggest complaint is 9.5 times out of 10 I have to manually shutdown and restart the box after any significant update. I'm just happy it's never bricked itself... I did have one of the WD Red 4T drives start to throw sector errors, but the replacement went very smooth and there was no data loss, although it took 26 hours to resilver the drive... The WD RMA process was a happy experience as well.
Synology is excellent in my books, but I'm a heavy user of several DS programs: Cloud Station Server/ ShareSync, DocuWiki, Hyper Backup, Snapshot Replication, and Web Station to host an external facing website via NGINX reverse-proxy. There's several file formats available; if you're only interested in simple storage then Synology is likely overkill.
For the more hands on enthusiast, check out FreeNAS or its fork NAS4free. Either will run on almost any hardware and uses software raid, so no raid card required. FreeNAS is the elephant and NAS4free is the mouse... I run NAS4free on 2 machines. One is an old X7SPA SuperMicro box with an Atom D525 processor, 4GB memory and 4x 4T reds but only at sata2; old & slow but very low power draw. The other is a VMware virtual machine on a Dell R420 server with 2 vcpus, 32GB ram, 4x 4T 12gbs SAS drives and a LSI9300 HBA passed through to the vm. Both instances have been bulletproof and hands-off since installation.